UC-NRLF 


SB    E77 


Edmund  O'Neill 


Massachusetts  Institute  of  Technology 


LABORATORY  EXPERIMENTS. 


tf  C^S^^/t*/  ff 


LABORATORY  EXPERIMENTS 


GENERAL  CHEMISTRY, 

COMPILED  FROM  ELIOT  AND  STOREYS  MANUAL 
AND  OTHER  SOURCES, 


11.  RIPLEY  NICHOLS  AND  LEWIS  II,  NORTON 


FOR   THE   USE   OF    STUDENTS    OF   THE    MASSACHUSETTS 
INSTITUTE   OF   TECHNOLOGY. 


REVISED  BY  FRED  L.  SARD  WELL. 


BOSTON,  MASS. 
1891. 


(\ 


O 


COPYRIGHT,  1884,  BY  W.  R.  NICHOLS. 


INTRODUCTION. 


As  this  pamphlet  may  fall  into  the  hands  of  teachers  and 
others  outside  of  the  Institute,  it  may  be  proper  to  say  a  few 
words  by  way  of  introduction. 

The  pamphlet  is  not  intended  to  be  used  without  a 
teacher. 

As  far  as  possible  the  directions  are  given  which  will 
enable  the  student  to  perform  the  experiments  successfully, 
but  he  is  left  to  make  his  own  observations,  and  then  to 
interpret  the  results,  with  such  aid  as  may  be  necessary  from 
the  instructors  who  are  always  present  in  the  laboratory. 
This  system,  which  was  introduced  by  Professor  Caldwell  in 
his  "  Introductory  Chemical  Practice,"  requires  a  careful 
inspection  of  the  laboratory  note-books. 

At  the  Institute  most  of  the  experiments  are  performed  on 
the  lecture  table  before  they  are  attempted  by  the  student, 
and  any  text-book  may  be  consulted  outside  the  laboratory; 
in  the  laboratory  itself  no  other  book  than  this  is  allowed. 
In  some  cases  a  sketch  of  the  necessary  apparatus,  or  an 
example  of  the  apparatus  itself,  is  placed  in  the  laboratory, 
where  it  can  be  seen  by  the  students. 


8897' 


TO    THE    STUDENT. 


UNLESS  special  directions  to  the  contrary  are  given,  no 
text-book  will  be  allowed  in  the  laboratory,  except  this 
pamphlet. 

The  laboratory  work  should  teach  us : 

(1)  To  observe  and   to   distinguish  essential   from   non- 
essential  phenomena ; 

(2)  To  express  in  writing  the  results  of  observation  ; 

(3)  To   draw  proper  conclusions   as  to  what  facts   are 
taught  by  the  experiments. 

The  student's  standing  is  largely  determined  by  the  qual- 
ity of  his  laboratory  work  and  note-book.  The  quality  is 
more  important  than  the  quantity,  and  one  experiment  well 
and  intelligently  performed  is  worth  more  than  a  dozen,  or, 
indeed,  than  any  number  of  experiments  performed  mechani- 
cally without  intelligence.  The  notes  must  be  written  clearly 
and  distinctly,  in  the  laboratory  note-books.  As  a  rule 
answer  concisely,  but  fully,  the  following  questions: 

(1)  What  materials  did  you  use  ? 

(2)  What  apparatus  did  you  use  ? 

(3)  What  did  you  do  ? 

(4)  What  did  you  observe  ? 

(5)  What  has  the  experiment  taught  you  ? 

Begin  the'  entry  for  each  day  with  the  date.  Do  not 
crowd  your  notes.  Leave  room  for  remarks,  additions,  or 
corrections.  Allow  a  paragraph  for  each  one  of  the  above 
headings. 


Make  the  record  of  an  experiment  as  soon  as  the  experi- 
ment is  performed,  and  present  the  notes  to  an  instructor 
for  examination  before  doing  other  work. 

It  is  not  expected  that  all  the  experiments  in  a  given  set 
will  be  performed  at  any  one  exercise  by  all  the  students, 
but  each  student  will  do  only  as  many  of  the  experiments  in 
the  set  as  he  can  do  well.  Leave  the  note-book  on  the  out- 
side of  the  desk  at  the  close  of  each  exercise. 

At  the  last  exercise  in  each  term  the  desks  should  be  left 
in  good  order.  No  allowance  is  made  for  apparatus  which  is 
not  in  proper  condition  to  be  served  out  to  other  students. 
No  allowance  is  made  for  files,  iron  pincers,  filters,  or  bits 
of  tubing. 


I  have  read  the  above  directions  carefully,  and  endeavored 
to  understand  them. 


(Name  here.)  .. 


MASSACHUSETTS  INSTITUTE  OF  TECHNOLOGY. 

First  Year. 
GENERAL    CHEMISTRY. 


EXERCISE    I.  —  PRELIMINARY   WORK. 

1.  Ascertain  the  number  of  your  desk. 

2.  Find  coat-hook  corresponding  to  your  desk. 

3.  Obtain  key  of  desk  at  the  supply  room. 

4.  Examine  contents  of  desk. 

5.  Hand  in  the  receipt  at  the  supply  room. 

6.  Take  the  piece  of  ignition  tubing  in  your  desk  and  report  to  one 
of  the  instructors. 

Experiment  1.  Mix  thoroughly  3  grams  of  coarsely  powdered  sul- 
phur with  8  grams  of  copper  filings  or  fine  turnings.  Put  the  mixture 
into  a  tube  of  hard  glass,  No.  3,  about  12  centimeters  long,  and  closed 
at  one  end.  (For  the  manipulation  of  tubing,  see  Appendix,  §§  1-4.) 
Hold  the  tube  by  the  open  end  with  the  wooden  nippers,  and  heat  the 
mixture  gently  over  the  gas  lamp.  When  no  further  change  takes  place, 
allow  the  tube  to  cool,  break  it,  and  examine  the  contents. 

2.  Heat  a  small  piece  of  lead  foil  on  the  lid  of  a  porcelain  crucible 
as  long  as  any  change  occurs.     Warm  slowly,  as  sudden  heat  will  cause 
the  porcelain  to  break.    While  this  is  going  on  perform  the  following : 

3.  Fit  to  any  small  flask  or  bottle  a  perforated  cork  (for  the  manip- 
ulation of  corks,  see  Appendix,  §  9),  to  which  has  been  adapted  a  short 
piece  of  glass  tubing,  No.  7.     Slip  over  the  end  of  this  glass  tube  a 
short  piece  of  caoutchouc  tubing.     Suck  part  of  the  air  out  of  the  flask, 
and  then  nip  the  caoutchouc  tube  with  thumb  and  finger,  so  that  no  air 
shall  re-enter.     Immerse  the  neck  of  the  flask  in  a  basin  of  water,  and 
release  the  caoutchouc  tube. 


8 


4»  -  T^ke  the«bpttle  a«  -prepared  for  Expt.  3,  and  into  the  upper  end 
of  trie  tnf  of  caoVtcftolact  ttibmg  insert  the  point  of  a  small  funnel.  Fill 
the  funnel  w.itl\  w^er  ;  Deport  -t'ltp  result  ;  loosen  the  cork  ;  report  what 


EXERCISE   2.  —  CHEMICAL  AND   PHYSICAL   CHANGES. 

5.  Burn  some  magnesium  wire,  observe  carefully  the  result  of  the 
combustion,  and  describe  the  product. 

6.  Mix  thoroughly  4  grams  of  powdered  sulphur  and  7  grams  of  fine 
iron  filings.     Examine  the  mixture  with  a  lens  ;  also  with  a  magnet  by 
putting  some  of  the  mixture  on  a  slip  of  paper,  and  passing  the  magnet 
to  and  fro  on  the  under  side  of  the  paper.     Now  heat  the  mixture  in 
an  ignition  tube  under  the  hood.     After  the  action  is  over,  break  the 
tube  and  examine  its  contents  with  lens  and  magnet.     Place  a  small 
portion  of  the  contents  in  a  test  tube,  and  pour  upon  it  i  c.  c.  of  dilute 
chlorhydric  acid  (HC1),  and  note  the  result.     Keep  careful  notes. 

7.  Heat  2  grams  of  red  oxide  of  mercury  in  a  matrass,  thrusting  into 
the  matrass  a  glowing  splinter  of  wood  from  time   to   time.    Observe 
carefully  all  that  happens. 

8.  Upon  a  small  piece  of  "quicklime"  put  a  few  drops  of  water. 
Note  the  result. 

9.  Heat  a  crystal  of  copper  sulphate  gently  on   a   crucible   cover. 
When  the  mass  is  cool,  add  a  drop  of  water,  holding  the  cover  in  the 
palm  of  the  hand. 

10.  Pour  into  a  test  tube  5  c.  c.  of  a  solution  of  copper  sulphate 
(CuSO4)  ;  add  4  or  5  drops  of  ammonia  water,  and  shake;  finally  add 
3  c.  c.  of  ammonia  water,  and  shake.     Record  all  that  you  observe. 

11.  Proceed  as  in  Expt.  10,  but  use  5  c.  c.  of  a  solution  of  acetate 
of  lead  and  i  c.  c.  of  a  solution  of  chromate   of  potassium  instead  of 
sulphate  of  copper  and  ammonia  water. 

12.  Warm  5  c.  c.  of  a  solution  of  potassium  permanganate  in  a  test 
tube  until  you  can  just  bear  your  hand  on  it  ;  then  add  three  or  four 
drops  of  dilute  sulphuric  acid,  and  finally  a  few  crystals  of  oxalic  acid. 

EXERCISE   3.  —  MANIPULATION    OF   GLASS. 

13.  Bend  glass  tubing  into  the  forms  shown  in  the  model.     Make  a? 
many  pieces  of  each  form  as  are  designated.     These   pieces  of  tubing 
should  be  saved,  as  they  are  all  to  be  used  in  subsequent  experiments. 


Show  your  work  to  an  instructor  and  have  it  approved,  before  doing 
jther  work.  For  instruction  in  glass  working,  read  Appendix,  pp.  3  to  5 
nclusive. 

EXERCISE  4.  —  HYDROGEN. 

14.  Make  a  small  cylinder  of  wire  gauze,  by  rolling  a  piece  of  fine 
*auze,  about  6  c.  m.  square,  around  a  thick  piece  of  No.  6  glass  tubing. 
Twist  fine  wire  around  the  cylinder  in  order  to  preserve  its  form ;  then 
slip  the  cylinder  off  the  glass  and  close  one  end  of  it  by  pressure  with  a 
stout  pair  of  pincers.     Within  this  cylinder  of  wire  gauze  place  a  piece 
of  metallic  sodium  as  large  as  a  pea,  and  then  close  the  upper  end  of  the 
cylinder  by  pressure  with  the  pincers,  as  before. 

Attach  the  wire  gauze  cage  firmly  to  the  end  of  a  piece  of  stout  iron 
wire,  and  thrust  it  quickly  into  the  water  pan,  so  that  the  cage  will  come 
directly  under  the  mouth  of  a  small  bottle  of  about  100  c.  c.  capacity, 
which  has  been  previously  filled  with  water,  and  is  held  inverted  in  the 
pan.  Gas  will  collect  and  is  to  be  tested  with  a  lighted  match. 

15.  Experiment  indicated  under  §  23.*    Take  an  iron  "gas  pipe" 
and  fill  the  middle  portion  with  bright  iron  turnings.     Rest  the  tube  on 
the  furnace  lamp  (without  the  iron  trough)  and  connect  one  end  with  the 
water  pan,  as  in  the  last  experiment.    The  other  end  is  connected,  by 
means  of  delivery  tubing  and  caoutchouc  connectors,  with   a  round- 
bottomed  flask,  half  full  of  water,  and  supported  on  a  ring  of  the  iron 
stand.     The  flask  should  rest  on  a  piece  of  wire  gauze,  and  the  bottom  of 
the  flask  should  be  about  4  or  5  c.  m.  above  the  top  of  the  Bunsen  lamp. 
Light  the  furnace  lamp,  and  wait  until  the  iron  pipe  has  become  red  hot ; 
then  heat  the  water  in  the  flask  until  it  boils  slowly.    As  the  steam 
passes  over  the  hot  iron  turnings  it  will  be  decomposed ;  a  gas  will  pass 
off  through  the  delivery  tube,  and  is  to  be  collected  in  bottles  at  the 
water  pan  as  soon  as  the  air  originally  contained  in  the  tubes  and  flask 
has  all  been  expelled.    Test  this  gas  with  a  lighted  match. 

16.  Prepare  a  hydrogen  generator  similar  to  the  pattern    shown. 
Within  the  bottle  put  15  or  20  grams  of  granulated  zinc,  or  small  scraps 
of  the  sheet  metal,  and  as  much  water  as  will  fill  about  one  quarter  of 
the  bottle.     Replace  the  cork  in  the  bottle,  taking  care  to  press  it  in 
tightly,  and  satisfy  yourself  that  the  apparatus  is  perfectly  tight  before 
proceeding  further.     Record  your  method  of  testing.     Then,  and  not  till 

*  Eliot  and  Storer's  Manual. 


10 


then,  gradually  pour  in  common  muriatic  acid  through  the  thistle  tube. 
The  thistle  tube  must  reach  nearly  to  the  bottom  of  the  bottle,  so  that  its 
point  may  dip  beneath  the  water ;  and  the  muriatic  acid  must  be  added 
by  small  successive  portions  —  not  more  than  a  large  thimbleful  at  a 
time.  On  the  addition  of  the  first  portions  of  the  acid,  chemical  action 
vill  ensue,  and  after  all  the  air  has  been  expelled  from  the  bottle,  the 
hydrogen  may  be  collected  over  the  water  pan  in  inverted  bottles  filled 
with  water.  The  moment  at  which  the  hydrogen  ceases  to  be  contami- 
nated with  air  can  be  determined  by  collecting  small  portions  of  the 
escaping  gas  in  wide-mouthed  bottles  of  about  50  c.  c.  capacity,  and  test- 
ing its  quality  by  means  of  a  lighted  match.  In  doing  this  the  small 
bottle  filled  with  gas  must  not  be  turned  over,  but  should  be  carefully 
lifted  from  the  water  without  changing  its  vertical  position,  and  the  lighted 
match  should  then  be  applied  to  the  mouth  of  the  bottle.  If  the  hydro- 
gen be  pure,  it  will  burn  tranquilly  at  the  mouth  of,  and  within,  the  bottle  ; 
but,  in  case  the  gas  is  still  mixed  with  much  air,  a  sharp  explosion  will 
occur  at  the  moment  when  the  match  is  touched  to  it.  In  experimenting 
with  hydrogen,  no  light  should  ever  be  brought  into  contact  with  the  con- 
tents of  the  bottle  in  which  it  is  generated,  or  with  any  large  quantity  of 
the  gas,  until  the  purity  of  the  sample,  or  rather  its  noa- explosive  charac- 
ter, has  been  demonstrated  by  applying  to  a  very  small  volume  of  the  gas 
the  test  above  described. 

17.  Carefully  lift  from  the  water  pan  a  bottle  of  200  or  300  c.  c. 
capacity,  completely  full  of  hydrogea  ;  slowly  carry  the  bottle,  the  mouth 
of  which  is,  of  course,  held  downward,  to  a  burning  candle  or  splinter  of 
wood,  and  depress  the  bottle  over  this  flame.     After  observing  what  hap- 
pens, withdraw  the  candle  slowly. 

18.  Take  a  glass  tube  3  or  4  c.  m.  in  diameter,  and  close  one  end  with 
a  plug  of  plaster  of  Paris  i  or  2  c.  m.  thick.     Set  the  tube  aside  to  dry 
until  the  next  exercise. 

EXERCISE    5. —  HYDROGEN. 

19.  Fill  the  plugged  tube  (prepared  at  the  last  exercise)  with  hydrogen 
by  upward  displacement,  taking  care  not  to  wet  the  plug.     Set  the  tube 
upright  in  a  bottle  of  water,  and  allow  it  to  remain  until  the  close  of  the. 
exercise,  noting  its  condition  from  time  to  time. 

20.  Over  a  jet  of  burning  hydrogen  hold  a  dry  cold  bottle. 


II 


21.  Introduce  two  volumes  of  hydrogen  and  five  volumes  of  air  into 
a  strong  bottle,  such  as  is  used  for  soda  water.     Close  the  mouth  of  the 
bottle  with  a  cork,  and  shake  violently,  in  order  that  the  gases  shall  be 
mixed.     A  small  quantity  of  water  should  be  left  in  the  bottle  to  act 
as  a  stirrer.     Grasp  the  bottle  firmly  in  one  hand,  remove  the  cork  with 
the  other,  and  apply  the  open  mouth  of  the  bottle  to  a  lighted  candle. 

22.  Light  a  small  jet  of  hydrogen.     Place  over  the  jet  a  piece  of 
ignition  tube  30  or  40  c.  in.  long,  and  move  the  jet  up  and  down  within 
the  tube  until  a  place  is  found  where  a  musical  tone  is  given. 

23.  Place  5  grams  of  copper  oxide  in  a  piece  of  ignition  tubing  about 
35  c.  m.  long ;  place  the  tube  upon  a  furnace  lamp,  heat,  and  pass  a 
stream  of  dry  hydrogen  through  the  tube  until  no  more  water  is  given  off. 
Allow  to  cool  and  weigh  the  contents  of  the  tube 

EXERCISE   6. — CHLORINE. 

[All  experiments  in  this  exercise  must  be  performed  under  the  hood.] 

24.  Place  in  a  test  tube  i  grain  of  potassium  bichromate  (K2Cr2O7). 
Pour  upon  it  10  c.  c.  of  hydrochloric  acid  (HC1),  and  warm  it.     Note 
the  result. 

25.  In  a  flask  of  about  500  c.  c.  capacity,  arranged  as  in  the  model 
on  the  desk,  place  8  or  10  grams  of  coarsely  powdered  manganese  binox- 
ide ;   pour  upon  it  50  or  60  c.  c.  of  common  muriatic  acid,  and  gently 
heat  the  mixture.     Chlorine  will  soon  be  disengaged,  and  may  be  recog- 
nized by  its  peculiar  color.     Fill  several  bottles  of  at  least  half  a  liter 
capacity  with  the  dry  gas,  by  displacement. 

It  is  necessary,  for  the  success  of  this  experiment,  that  the  gas  be 
thoroughly  dried  ;  this  is  effected  by  heating  the  flask  containing  the 
manganese  binoxide  and  chlorhydric  acid  gently,  and  passing  the  chlo- 
rine through  a  tube  filled  with  chloride  of  calcium  or  other  substances 
which  will  absorb  moisture.  Gradually  sift  a  gram  or  two  of  very  finely 
powdered  metallic  antimony  into  one  bottle. 

Drop  a  piece  of  Dutch  metal  foil  into  a  jar  of  chlorine. 

Introduce  a  thin  slice  of  phosphorus  into  a  bottle  of  dry  chlorine. 

Into  another  bottle  of  chlorine  thrust  a  burning  taper  or  a  bit  of 
flaming  wood  or  paper,  or  better  a  burning  candle. 


12 


26.  Generate  hydrogen  as  in  Expt.  16;  when  the  hydrogen  is  found 
by  testing,  to  be  pure,  connect  with  the  generator  a  tube  drawn  to  a  fine 
point.     Light  this  jet  of  hydrogen  and  immerse  it  in  a  bottle  of  chlorine. 
Apply  a  piece  of  litmus  paper  to  the  sides  of  the  bottle. 

Repeat,  using  a  jet  of  illuminating  gas. 

27.  In  a  soda  water  bottle  mix  equal  volumes  of  chlorine  and  hydro- 
gen ;  then  remove  the  cork  and  hold  the  mouth  of  the  bottle  in  the  flame 
of  a  lamp. 

28.  Suspend  a  piece  of  calico  in  a  jar  of  perfectly  dry  chlorine.     See 
if  there  is  any  change.     Now  wet  the  calico  ;  and  again  suspend  it  in  the 
chlorine.     Explain  the  result. 

EXERCISE   7. — CHLORINE. 

29.  At  the  bottom  of  a  large,  tall  bottle,  or  other  wide-mouthed  glass 
vessel,  of  the  capacity  of  two  or  three  liters,  place  a  small  bottle  contain- 
ing 15  or  20  grams  of  bleaching  powder.     Cover  the  beaker  with  a  glass 
plate  or  sheet  of  pasteboard,  provided  with  a  small  hole  at  the  center ; 
through  this  hole  in  the  cover  pass  a  thistle  tube  down  into  the  bottle  of 
bleaching   powder  and  pour  upon  it  several  small  successive  portions 
of  sulphuric  acid  diluted  with  an  equal  volume  of  water.     Chlorine  gas 
will  immediately  be  set  free  and  is  to  be  ladled  out  of  the  jar  with  a 
dipper  made  of  a  small  bottle  and  poured  upon  a  solution  of  indigo  to 
show  its  bleaching  power. 

30.  Soak  a  bit  of  printed  calico  in  a  half  liter  of  water,  into  which  10 
or  15  grams  of  bleaching  powder  have  been  stirred.     After  a  short  time 
transfer  the  cloth  to  another  bottle  filled  with  very  dilute  chlorhydric  or 
sulphuric  acid.     Finally,  wash  the  cloth  thoroughly  in  water. 

31.  Pour  into  a  test  tube  a  quantity  of  chlorine  water ;  drop  into  it  a 
small  quantity  of  a  solution  of  indigo,  and  stir  the  mixture  with  a  glass 
rod.     Repeat  with  solutions  of  aniline  red,  aniline  violet,  cochineal,  log- 
wood, and  potassium  permanganate. 

After  you  have  performed  all  the   above  experiments,  perform  any 
which  you  may  have  omitted  in  the  previous  exercise. 


EXERCISE  8.  — BROMINE   AND   IODINE. 

32.  From  an  assistant  receive  into  a  flask  or  bottle  of  I  or  2  liters 
capacity  3  or  4  drops  of  bromine.     Cover  the  bottle  loosely  and  leave 
it  standing ;  immerse  a  piece  of  moist  litmus  paper  in  the  gas. 

33.  Warm  gently  a  few  crystals  of  KBr  with  0.2  gram  MnO2  and  i 
c.  c.  H2SO4  in  a  test  tube  and  observe  the  vapor.     (Under  the  hood.) 

34.  Take  5  c.  c.  of  bromine  water  in  a  tube  and  warm  under  the 
hood.     Observe  what  happens.     Test  the  remaining  liquid  with  litmus 
paper. 

35.  Receive  a  few  drops  of  dry  bromine  in  an  ignition  tube;  throw 
upon  it  a  little  powdered  antimony. 

36.  Hold  a  dry  test  tube  in  the  gas  lamp  by  means  of  the  wooden 
nippers  and  warm  it  along  its  entire  length,  in  so  far  as  this  is  practica- 
ble.    Drop  into  the  hot  tube  a  small  fragment  of  iodine. 

37.  Prepare  a   quantity  of  thin  starch  paste  by  boiling  30  c.  c.  of 
water  in  a  porcelain  dish  and  stirring  into  it  0.5  gram  of  starch  which 
has  previously  been  reduced  to  the  consistency  of  cream  by  rubbing  it  in 
a  mortar  with  a  few  drops  of  water.    Note  the  change  in  the  starch. 

38.  Pour  3  or  4  drops  of  the  paste  into  10  c.  c.  of  water  in  a  test 
tube,  and  shake  the  mixture  so  that  the  paste  may  be  equably  diffused 
through  the  water ;  then  add  a  drop  of  an  aqueous  solution  of  iodine. 
Heat  the  solution  gently  until  the  color  disappears,  and  allow  it  to  cool 
again.      This    action   affords   a   delicate  test   for  iodine   when   not   in 
combination. 

39.  Dip  a  strip  of  white  paper  in  the  starch  paste  and  suspend  it, 
while  still  moist,  in  a  large  bottle,  into  the  bottom  of  which  two  or  three 
crystals  of  iodine  have  been  thrown.     What  does  the  experiment  show  ? 

40.  To  a  portion  of  the  starch  paste  made  in  Expt.  37  add  a  few 
drops  of  potassium  iodide  solution.     Into  the  paste  thus  prepared  clip 
strips  of  filter  paper.     This  is  "  iodo-starch  paper." 

41.  Repeat  Expt.  38,  using  bromine  water  instead  of  the  aqueous 
solution  of  iodine. 

42.  Put  i  gram  of  MnC>2  in  a  test  tube,  pour  upon  it  i  c.  c.  of  HC1, 
and  warm  gently.     Now  hold  a  piece   of  iodo-starch   paper  over   the 
tube  and  notice  the  result.     Explain  the   action.     This   affords   a  test 
for  chlorine. 

43-     Take  a  very  dilute  solution  of   potassium  iodide,  add  a   little 
carbon  bisulphide  and  a  few  drops  of  chlorine  water;   shake   up  and 


14 

then  allow  to  stand  for  a  few  moments.  Repeat,  using  potassium  bro- 
mide instead  of  the  iodide.  Chloroform  may  be  used  instead  of  carbon 
bisulphide.  Their  action  is  merely  mechanical.  This  shows  how  we 
may  recognize  bromine  and  iodine  in  compounds. 

EXERCISE  9. —  IODINE  AND   FLUORINE. 

44.  Place  0.25  gram  of  finely  powdered  iodine  in  a  porcelain  capsule, 
pour  upon  it  enough  concentrated  ammonia  water  to   somewhat   more 
than  cover  the  iodine,  and  allow  the  mixture  to  stand  during  15  or  20 
minutes  with  occasional  stirring.     Collect  in  several  small  filters  (Appen- 
dix, §  15)  the  insoluble  dark  brown  powder  which  will  be  found  at  the 
bottom  of  the  liquid.    Wash  well  with  cold  water  and  then  remove  the  fil- 
ter ;,   together  with   their   contents,  from  the   funnels;    pin  them  upon 
bits  of  board  and  allow  them  to  dry  spontaneously.     The  powder  is  the 
nitrogen   iodide.      As  soon   as  it   has   become  thoroughly  dry,  it   will 
explode   upon  being  rubbed,  even  with  a  feather,  or  jarred,  as  by  the 
shutting  of  a  door  or  by  a  blow  upon  the  wall  or  table. 

45.  [Under  the  hood.]     Warm  a  slip  of  glass  and  rub  it  with  bees- 
wax so  that  it  shall  be  everywhere  covered  with  a  thin,  uniform  layer  of 
the  wax.     With  a  needle,  or  other  pointed  instrument,  write  a  name,  or 
trace  any  outline  through  the  wax,  so  as  to  expose  a  portion  of  the  glass. 
Lay  the  etching,  face  downward,  upon  a  bowl  or  trough  of  sheet-lead,  in 
which  has  been  placed  a  teaspoonful  of  powdered  fluor-spar  and  enough 
strong  sulphuric  acid  to  convert  it  into  a  thin  paste. 

Cover  the  glass  and  the  top  of  the  dish  with  a  sheet  of  paper,  and  then 
heat  the  leaden  vessel  for  a  few  moments  very  gently,  taking  care  not  to 
melt  the  wax  ;  then  set  the  dish  aside  in  a  warm  place  and  leave  it  at 
rest  until  the  end  of  the  exercise.  Finally,  melt  the  wax  and  wipe  it  off 
the  glass  with  a  towel  or  bit  of  paper. 

46.  Into  a  perfectly  dry  matrass  put  a  small  quantity  of  a  mixture  of 
equal  parts  of  quartz  and  powdered  fluor-spar.     Moisten  with  a   drop 
of  strong  sulphuric  acid  and  heat  in  the  flame  of  the  lamp.     Hold  a 
drop  of  water  in  a  loop  of   platinum  wire  at  the  mouth  of  the  tube. 
Show  Vesult  and  ask  for  explanation.     This  shows  how  we  may  recognize 
fluorides.     The  experiment  will  be  performed  in  a  subsequent  exercise, 
and  will  then  be  fully  explained. 


EXERCISE    10.  —  CHLORHYDRIC   ACID. 

47.  Put  30  grams  of  dry,  coarse  salt  into  a  flask  of  a  liter  capacity. 
Arrange  the  apparatus  as  shown  in  the  pattern.     When  you  are  sure  that 
the  apparatus  is  all  right,  pour  50  grams  of  strong  sulphuric  acid  upon  the 
salt,  and  immediately  cork  the  flask,  place  it  upon  a  sand  bath   on 
the  iron  stand  and  connect  the  delivery  tube  with  the  Woulfe  bottles. 

Be  sure  that  the  tube  from  the  flask  does  not  dip  into  the  water  of  the 
first  bottle.  The  contents  of  the  flask  must  be  very  gradually  and  mod- 
erately heated,  else  a  violent  frothing  is  liable  to  occur,  which  would 
spoil  the  experiment.  In  your  notes  describe  the  apparatus ;  and  show 
the  use  of  safety  tubes. 

48.  Perform  Expt.  47,  and  while  the  gas  is  coining  off  disconnect 
the  flask  for  a  moment  and  bring  an  open  bottle  of  NH^HO  into  the 
neighborhood.     Also,  while  the  experiment  is  going  on,  put  into  sepa- 
rate test  tubes  small  fragments  of  CaCl2  and  NH4C1,  cover  with  strong 
H2  SC>4,  warm  gently  and  test  for  evolved  gas  by  smell  and  by  moistened 
red  and  blue  litmus  paper. 

49.  Pour  a  few  c.  c.  of  the  contents  of  the  Woulfe  bottle  nearest  the 
flask  into  a  test  tube,  add  a  strip  of  zinc  and  note  the  result. 

50.  To  5  c.  c.  of  the  contents  of  the  first  Woulfe  bottle  add  5  drops 
of  a  solution  of  silver  nitrate  (AgNOs)  and  shake  violently,  and  note  the 
result.     Save  the  contents  of  the  test  tube.     Put  it  into  the  jar  provided 
marked  "silver  residues." 

51.  Into  each  of  two  test  tubes  put  a  small  bit  of  gold  leaf.     Into 
one  test  tube  put  one  or  two  c.  c.  of  strong  nitric  acid  ;  into  the  other  put 
an  equal  quantity  of  strong  chlorhydric  acid.     Warm   gently.     Finally 
mix  the  contents  of  the  two  tubes.     The  mixture  of  nitric  and  chlorhy- 
dric acid  is  known  as  aqua  regia. 

52.  Place  10  c.  c.  of  a  solution  of  acetate  of  lead  in  a  test  tube  and 
add  dilute  HC1  until  no  further  precipitation  takes  place.     Let  the  pre- 
cipitate settle,  then  pour  off  the  liquid;   add  ten  cr. c.  of   water  to  the 
precipitate  and  boil  for  a  minute  or  two,  and  then  filter  quickly  but  care- 
fully, receiving  the  filtrate  in  a  clean  test  tube  kept  warm  by  being  im- 
mersed in  a  beaker  of  hot  water.     When  the  liquid  has  filtered  through, 
remove  test  tube  from  the  hot  water  and  allow  to  cool. 


i6 


EXERCISE  II.  — OXYGEN   AND  OZONE. 

53.  In  a  clean  bottle  of  i  or  2  liters  capacity  place  a  piece  of  phos- 
phorus 2  or  3  c.  m.  long,  the  surface  of  which  has  been  scraped  clean 
(under  water)  with  a  knife ;  pour  water  into  the  bottle  until  the  phos- 
phorus is  half  covered  ;  cover  the  bottle  with  a  plate  of  glass  and  set  it 
aside  in  a  place  where  the  temperature  is  20°  or  30°.     Observe  the  ap- 
pearance and  odor  of  the  contents  of  the  bottle  after  15  or  20  minutes. 
Suspend  in   the  bottle  a  strip  of  iodo-starch  paper,  and  also  a  strip 
of  red  litmus  paper  which  is  saturated  with  potassium  iodide  solution. 
Explain  the  results.     During  this  experiment  perform  those  following. 

54.  Mix  intimately  5  grams  of  potassium  chlorate  with  5  grams  of 
"black   oxide   of  manganese,"  which  has  been   previously  well   dried. 
Place  the  mixture  in  a  tube  of  hard  glass,  No.  I,  12  or  15  c.  m.  in  length. 
Attach  to  this  ignition  tube,  by  means  of  a  perforated  cork  or  caoutchouc 
stopper,  a  delivery  tube  of  glass,  No.  7,  as  in  the  model.     Heat  the  mix- 
ture in  the  ignition  tube,  and  collect  the  gas  which  will  be  given  off  in 
bottles  or  jars  of  the  capacity  of  about  250  c.  c.     The  first  100  c.  c.  or  so 
of  gas  should  be  rejected,  since  it  will  be  contaminated  with  the  air  origi- 
nally contained  in  the  apparatus.     Collect  at  least  five  bottles  and  one 
test  tube  full  of  the  gas  for  subsequent  experiments. 

In  performing  this  experiment  the  following  precautions  should  be 
observed:  i.  Both  the  potassium  chlorate  and  the  manganese  binoxide 
should  be  perfectly  dry  and  pure ;  that  is,  free  from  moisture,  dust  or 
particles  of  organic  matter.  They  should  not  be  ground  together  under 
any  circumstances. —  DANGER  !  2.  As  soon  as  the  gas  begins  to  be 
delivered,  the  heat  beneath  the  ignition  tube  should  be  diminished,  if 
need  be,  and  so  regulated  that  the  evolution  of  gas  shall  be  tranquil  and 
uniform.  3.  The  uppermost  portions  of  the  mixture  should  be  heated 
before  the  lower.  4.  The  ignition  tube  should  never  be  filled  to  more 
than  one  third  its  total  capacity,  lest  solid  matter  be  projected  into  the 
delivery  tube,  and  the  outlet  for  the  gas  be  thus  stopped.  5.  The  igni- 
tion tube  should  always  be  inclined  and  never  placed  upright  in  the 
flame. 

Place  in  a  deflagrating  spoon  a  bit  of  sulphur  as  large  as  a  pea.  Light 
the  sulphur  and  thrust  it  into  a  bottle  of  oxygen. 

Burn  a  bit  of  phosphorus  in  oxygen  in  a  similar  manner,  but  with  much 
greater  care. 


Place  a  piece  of  charcoal  —  that  of  bark  is  best  —  in  a  deflagrating 
spoon.  Kindle  the  charcoal  by  holding  it  in  the  flame  of  a  lamp  and 
then  introduce  it  into  a  bottle  of  oxygen. 

Make  into  a  spiral  coil  some  fine  iron  wire  —  or,  better,  a  watchspring, 
which  has  been  rendered  flexible  by  igniting  it  and  allowing  it  to  cool 
slowly  —  and  to  the  end  attach  a  bit  of  tinder  or  the  tipped  end  of  a 
match.  Light  the  kindling  material  and  plunge  the  spiral  into  a  jar  of 
oxygen  in  the  bottom  of  which  an  inch  or  so  of  water  has  been  left. 

55.  Support  a  rather  wide  tube  of  thin  glass  —  the  neck  of  a  broken 
retort,  for  example  —  in  a  vertical  position  and  connect  the  upper  open- 
ing with  a  gas  generator  from  which  hydrogen  is  being  evolved.     Allow 
the  gas  to  flow  until  the  tube  is  filled  ;  then  apply  a  lighted  match  to  the 
mouth  of  the  tube,  and  regulate  the  flow  of  gas  so  that  the  latter  may 
continue  to  burn  slowly  at  the  lower  edge  of  the  tube.     Meanwhile,  pre- 
pare some  oxygen  as  in  Expt.  54,  connecting  the  ignition   tube  with  a 
piece  of  narrow  glass  tubing,  drawn  out  to  a  fine  point;  and,  while  the 
oxygen  is  flowing  through  this  tube,  pass  it  up  into  the  larger  tube  filled 
with    hydrogen.     This    experiment  should  be   performed  by  two  stu- 
dents together  as  will  be  directed. 

56.  Dissolve   a  bit  of  potassium  hydrate  (KOH)  hi   a  few  c.  c.  of 
water,  add  a  teaspoonful  of  pyrogallic  acid,  and  pour  the  solution  into 
the  test  tube  containing  the  O,  taking  care  that  the  O  shall  not  escape. 
Place  the  thumb  over  the  end  of  the  tube  and  shake.     Notice  the  result. 
Place  the  mouth  of  the  tube  under  water  and  remove  the  thumb,  and 
observe  what  happens. 

57.  Heat  some  black  oxide  of  manganese  in  a  small  matrass  in  the 
blast  lamp,  and  see  whether  oxygen  is  evolved. 

EXERCISE    12. — SULPHUR. 

58.  Place  in  a  test  tube,  of  about  30  c.  c.  capacity,  15  to  20  grams  of 
coarsely  powdered  sulphur  ;  melt  the  sulphur  slowly  over  the  gas  lamp, 
and  continue  to  heat  it  until  it  begins  to  boil,  noting, '  meanwhile,  the 
changes  which  the  sulphur  undergoes.     Finally,  pour  the  hot  sulphur, 
in  a  fine  stream,  into  a  large  dish  full  of  cold  water,  and  examine  its 
appearance. 

59.  In  a  small  beaker  glass,  or  Hessian  crucible,  slowly  heat  50  to 
60  grams  of  sulphur  until  it  has   entirely  melted.     Remove  the   vessel 
from  the  lamp  and  allow  it  to  cool  slowly  until  about  a  quarter  part  of 


i8 


the  sulphur  has  solidified;  then  pour  off  into  a  basin  of  water  that  por- 
tion of  the  sulphur  which  is  still  liquid,  breaking  through,  for  this  pur- 
pose, the  crust  at  the  top  of  the  liquid,  if  any  such  have  formed.  Show 
the  result. 

60.  In  a  test  tube,  melt  enough  sulphur  to  fill  one  quarter  of  the 
tube ;  place  the  tube  in  such  a  position  that  its  contents  may  cool  slowly 
and  quietly,  and  then  watch  the  formation  of  crystals  as  they  shoot  out 
from  the  comparatively  cold  walls  of  the  tube  towards  the  center  of  the 
liquid. 

61.  Place  i  gram  of  sulphur  in  a  dry  test  tube  and  pour  upon  it 
5  c.  c.  of  carbon  bisulphide,  cork  tightly,  and  shake  for  a  few  moments. 
[Carbon  bisulphide  is  volatile  and  VERY  INFLAMMABLE.    HAVE  NO  LIGHTS 
NEAR  BY.]     Pour  a  little  of  the  clear  solution  upon  a  watch  glass  and 
allow  the  carbon  bisulphide  to  evaporate  under  the  hood.     Examine  the 
residue  obtained. 

62.  Place  a  few  bits  of  sulphur  in  a  perfectly  dry  test  tube  and  heat 
gradually  until  the  sulphur  boils.     Notice  the  sublimate. 

63.  Mix  intimately  4  grams  of  flowers  of  sulphur  and  7  grams  of  the 
finest  iron  filings.     Place  the  mixture  in  an  ignition  tube  10  to  12  c.  m. 
long,  and  heat  the  lower  end  of  the  tube  gently  over  the  gas  lamp  under 
the  hood.     When  chemical  action  once  begins,  take  the  tube  out  of  the 
flame.     Don't  be  surprised  if  the  tube  breaks. 

64.  Heat  a  gram  or  so  of  sulphur  in  an  ignition  tube  until  it  boils, 
and  allow  a  few  bits  of  copper  filings  to  fall  into  the  melted  sulphur. 

65.  Heat  some  powdered  pyrite  in  a  matrass. 

EXERCISE  13.  —  HYDROGEN  SULPHIDE. 

66.  Put   10  or   12  grams  of  iron  sulphide  into  a  generator  bottle. 
Arrange  the   delivery  tube  so  that  it  shall  dip  beneath  the  surface  of 
water  contained  in  another  (smaller)  bottle.     Through  the  thistle  tube, 
pour  into  the  gas  bottle  water  enough  to  seal  the  lower  extremity  of  this 
tube ;  then  add,  through  the  thistle  tube  as  before,   10  c.  c.  of  strong 
chlorhydric  acid,  and  observe.     When  the  disengagement  of  gas  slackens, 
a  new  portion  of  chlorhydric  acid  may  be  added  through  the  thistle  tube, 
and  this  process  continued  until  the  water  in  the  absorption  bottle  smells 
strongly  of  the  gas. 

[The  experiment  must  be  performed  under  the  hood.] 


19 

67.  To  the  delivery  tube  of  the  gas  bottle  employed  in  generating 
hydrogen  sulphide,  attach  a  drying  tube  containing  fragments  of  calcium 
chloride,  and  with  the  tube  connect  a  piece  of  No.  6  glass  tubing  drawn 
out  to  a  fine  point.     When  the  apparatus  is  full  of  the  gas,  apply  a  match 
to  the  end  of  the  tube.     The  gas  will  take  fire.     Hold  a  dry  bottle  over 
the  flame,  and  test  the  deposited  moisture  with  litmus  paper. 

68.  Put  a  drop  of  sulphureted  hydrogen  water  on  a  bright  piece  of 
lead,  copper,  or  silver. 

69.  Dissolve  a  small  crystal  of  lead  nitrate  in  a  test  tube  half  full  of 
water,  and  to  this  solution  add  a  few  drops  of  the  sulphureted  hydrogen 
water. 

70.  Take  20  c.  c.  of  a  solution  of  each  of  the  following  substances  : 
CuSO4,  As2O3,  SbCl3,  ZnSO4,  MnSO4,  K2SO4.     Place  each  solution  in 
a  separate  test  tube  and  saturate  each  with  H2S.    Have  solutions  boiling 
hot.     Provide  a  short  piece  of  delivery  tube  for  each  test  tube,  so  that 
there  will  be  no  danger  of  mixing  the  solutions.     Observe  what  happens; 
write  the  reactions.     Then  add  I  c.  c.  strong  HC1  to  each  tube,  shake, 
and  observe  the  effect. 

71.  Moisten  a  piece  of  filter  paper  with  acetate  of  lead  solution  and 
hold  it  near  the  delivery  tube  of  an  H2S  generator.     This  is  the  test  for 
H2S. 

72.  Pass  H2S  through  10  c.c.  of  HNO3  (i  :  i). 

73.  Prepare  apparatus  exactly  as  in  Expt.  67,  except  make  the  tube 
which  ends   in  the  jet  straight  and  about   20  c.  m.  long.     Heat  this 
tube  gently  with  the  Bunsen  burner  near  the  center  while  a  stream  of 
H2S  is  passing  through  it,  and  observe  the  tube  carefully. 

EXERCISE   14. — NITROGEN. 

74.  Into  a  small  porcelain  capsule,  supported  on  a  piece  of  stout 
iron  wire  as  will  be  shown,  put  about  a  cubic  centimeter  of  phosphorus, 
and  set  it  on  fire.     Invert  over  the  capsule  a  wide-mouthed  bottle,  of  the 
capacity  of  a  liter  or  more,  and  hold  this  bottle  so  that  its  mouth  shall 
dip  beneath  the  surface  of  the  water.     The  dense  white  cloud  which  fills 
the  bottle  at  first  is  a  compound  of  phosphorus  and  oxygen,  which  is 
soluble  in  water.     It  will,  therefore,  soon  be  absorbed  by  the  writer  in 
the  pan,  and  will  disappear.     Remove  the  wire  with  the  capsule,  which 
may  be  readily  done  by  tipping  the  bottle  to  one  side,  taking  care  that 
the  mouth  does  not  come  out  of  the  water,  and  slip  a  glass  plate  under 


2O 


the  mouth  of  the  bottle ;  invert  the  bottle  so  that  it  stands  upright,  and 
thrust  a  burning  splinter  of  wood  or  a  lighted  candle  into  the  gas. 

75.  Take  a  piece  of  ignition  tubing  about  35  centimeters  long,  and 
introduce  into  it  enough  copper  turnings  to  fill  loosely  about  15  centim- 
eters of  its  length.     Support  the  tube  upon  one  of  the  "  furnace  lamps," 
resting  the  tube  in  an  iron  trough.     Into  one  end  of  the  tube  fit  a  cork 
through  which  passes  a  bent  delivery  tube  leading  to  the  water  pan ;  con- 
nect the  other  end  of  the  tube  with  a  "gasholder  bottle  "  similar  to  that 
shown  in  the  model.     Light  the  furnace  lamp  and  heat  the  tube  gently 
until  the  iron  trough  becomes  red  hot.     Then  pass  a  slow  current  of  air 
over  the  heated  copper,  which  is  accomplished  by  pouring  water  into  the 
gasholder  bottle.     Collect  in  bottles   the  gas   which    is    delivered  at 
the  water  pan,  and  test  it  with  lighted  splinters. 

76.  Put  3  c.  c.  of  ammoniacal  cuprous  chloride  into  a  test  tube,  close 
the  end  with  the  thumb,  and  shake  vigorously.     Invert  the  tube  in  the 
water  pan  and  remove  the  thumb.    Note  the  result.    Test  the  gas  remain- 
ing in  the  tube  with  a  lighted  splinter. 

77.  Determine  accurately  the  contents  of  a  narrow  test  tube  in  cubic 
centimeters  by  filling  it  with  water  from  a  burette,  and  pour  into  the  test 
tube  exactly  5  c.  c.  of  potassium  pyrogallate  solution.     Shake  carefully 
for  several  minutes,  keeping  the  tube  tightly  closed  with  the  thumb. 
Now  open  under  water  as  in  Expt.  56,  and  allow  the  water  to  rise.     Then 
place  the  thumb  underneath  the  tube  and  raise  it  from  the  pan  and  invert 
it,  still  holding  the  thumb  over  the  end.     Determine  the  volume  of  the 
unabsorbed  gas  by  filling  the  tube  with  water  from  a  burette.     Calculate 
the  percentage  of  oxygen  in  the  air  by  volume. 

EXERCISE    15. — AMMONIA. 

78.  Mix  thoroughly  25  grams  of  ammonium  chloride  with  an  equal 
weight  of  cold  freshly  slaked  lime.     Place  the  mixture  in  a  flask  of  500 
c.  c.  capacity,  cover  with  water,  connect  with  a  couple  of  Woulfe  bottles, 
as  shown  in  the  pattern,  and  then  heat  the  flask.     Describe  the  apparatus 
and  explain  the  action  of  the  various  tubes.     When  the  experiment  is 
finished,  examine  the   contents  of  the  Woulfe  bottles.      Perform  the 
experiment  under  the  hood  if  possible. 

79.  While  Expt.  78  is  going  on,  disconnect  the  flask  for  a  moment 
and  bring  an  open  bottle  of  strong  HC1  into  the  neighborhood.     Also, 
fill  a  test  tube  with  the  gas  —  by  upward  displacement  —  close  the  mouth 


21 


tightly  with  the  thumb,  place  the  tube,  mouth  downwards,  in  a  vessel  of 
water,  and  then  remove  the  thumb. 

80.  Mix  together  equal  quantities  of  NH^NOs  and  CaH^O^  and 
heat  gently  in  a  test  tube.  Test  for  evolved  gas  by  smell  and  by  mois- 
tened red  litmus  paper.  Also  put  a  little  solid  NH^Cl  and  NH^NOg  into 
separate  test  tubes,  cover  with  a  solution  of  NaHO  in  each  case,  and 
warm  gently,  testing  as  in  previous  instance. 

82.  Heat  in  an  ignition  tube  7  grams  of  fine  iron  filings  and  0.5  gram 
powdered  KOH.     Collect  the  gas  in  test  tubes  over  the  water  pan,  and 
test  it  with  lighted  splinter.     Perform  the  same  experiment  with  7  grams 
of  coarse  iron  filings  and  0.5  gram  KNO3.     Now  heat  a  mixture  of  14 
grams  coarse  iron  filings,  0.5  gram  KOH  and  0.5  gram  KNOa  in  a  large 
test  tube,  and  test  the  gas  evolved  as  in  Expt.  79. 

EXERCISE    l6. — PHOSPHORUS. 

[Extreme  care  must  be  taken  in  all  experiments  with  phosphorus.] 

83.  Put  a  piece  of  phosphorus  as  big  as  a  grain  of  wheat  upon  a 
piece  of  filter  paper  and  sprinkle  over  it  some  lamp-black  or  powdered 
bone-black.     Allow  it  to  stand  for  a  while. 

84.  In  a  narrow  glass  tube,  No.  6,  about  30  c.  m.  long  and  closed  at 
one  end,  place  a  quantity  of  red  phosphorus  as  large  as  a  small  pea; 
heat  the  phosphorus  gently  over  the  gas  lamp  and  note  the  character  of 
the  sublimate  which  forms.     When  the  tube  is  perfectly  cold,  cut  it 
off  just  below  the  sublimate  and  scratch  the  coating  with  an  iron  wire. 

86.  In  order  to  observe  the  comparative  difficulty  of  inflaming  red 
phosphorus,  lay  an  inverted  cover  of  a  porcelain  crucible  upon  an  iron 
triangle  upon  the  lamp  stand ;  place  upon  the  cover,  at  some  distance 
from  each  other,  a  small  bit  of  ordinary  phosphorus  and  an  equal  quan- 
tity of  red  phosphorus  ;  heat  the  cover  gently  and  gradually  over  the 
gas  lamp.  [This  experiment  should  be  performed  under  the  hood,  if 
possible.] 

86.  In  a  thin-bottomed  flask  of  about  140  c.  c.  capacity,  put  I  gram 
of  phosphorus  and  115  c.  c.  of  hydrate  of  sodium,  obtained  by  dissolving 
40  grams  of  common  caustic  soda  in  noc.  c.  of  water.  Pour  two  or 


three  drops  of  ether  upon  the  liquid  in  the  flask,  then  close  the  flask 
with  a  cork  carrying  a  long  delivery  tube  of  glass,  No.  5.  Place  the 
flask  over  the  gas  lamp  upon  a  piece  of  wire  gauze,  and  immerse  the  end 
of  the  delivery  tube  in  the  water  pan ;  then  gently  heat  the  flask.  The 
ether  is  added  in  order  that  the  last  traces  of  air  may  be  expelled  from 
the  flask  by  the  heavy  vapor  into  which  this  highly  volatile  liquid  is 
converted  as  soon  as  it  is  warmed.  As  soon  as  bubbles  of  gas  begin  to 
be  expelled,  the  heat  should  be  moderated  or  the  lamp  wholly  removed. 
Perform  the  experiment  under  the  hood,  if  possible. 

EXERCISE   i;.  — SULPHUROUS  ANHYDRIDE. 

87.  Light  a  piece  of  sulphur  in  a  deflagrating  spoon  and  suspend  the 
latter  in  a  two  liter  bottle  full  of  air.     Observe  the  odor.     Immerse  a 
lighted  taper  in  the  gas  obtained. 

88.  Place  a  pinch  of  copper  filings  in  a  test  tube,  cover  with  con- 
centrated 113804,  and  warm  GENTLY.     Observe  the  odor  of  SOg.     En- 
deavor to  bleach  a  rose  or  other  flower,  previously  moistened,  by  holding 
it  in  the  fumes. 

89.  Repeat  Expt.  88,  but  use  charcoal  in  the  place  of  the  copper. 

90.  Charge  a  bottle,  of  the  capacity  of  a  liter  or  more,  with  sulphur- 
ous acid  by  burning  in  it  a  bit  of  sulphur.     Fasten  a  shaving,  or,  better, 
a  tuft  of  gun-cotton,  upon  a  glass  rod  or  tube  bent  at  one  end  in  the  form 
of  a  hook ;  wet  the  shaving  in  concentrated  nitric  acid,  and  hang  it  in  the 
bottle  of  sulphurous  acid.     Interpret  what  you  observe. 

Pour  a  little  BaCl2  solution  into  the  bottle  before  beginning  the 
experiment,  and  notice  its  condition  at  the  end  after  shaking  the  bottle. 
Write  the  reaction. 

91.  Arrange  a  generator  flask  as  shown  in  the  model.     Place  in  the 
bottom  15  grams  of  charcoal  and  add  50  c.  c.  of  concentrated  H2SO4. 
Warm  gently  upon  a  sand  bath,  and  SOg  will  be  evolved.     Place  5  grams 
of   PbO2  in  a  piece  of  ignition  tube,  and  pass   a  slow  current  of  SO2 
through  the  tube,  and  at  the  same  time  heat  the  tube  containing  the 
PbOg  moderately  upon  a  furnace  lamp.    Perform  this  experiment  imder 
the  kood. 


EXERCISE    l8.  —  SULPHURIC   ACID. 

92.  Place  in  a  pint  bowl  30  c.  c.  of  water;  pour  gradually  into  the 
water  120  grams  of  concentrated  sulphuric  acid,  stirring  the  mixture  with 
a  narrow  test  tube  containing  a  few  c.  c.  of  water.     So  much  heat  will  be 
evolved  during  the  union  of  the  water  and  the  acid  that  the  water  in  the 
test  tube  may  actually  boil.     Save  the  dilute  acid.        * 

93.  Pour  30  grams  of  strong  H2SC>4  upon   120  grains  of  snow,  and 
observe  the  temperature  of  the  mixture  with  the  thermometer. 

94.  Repeat  Expt.  93,  but  use  120  grams  of  H2SC>4  and  30  grams  of 
snow.     Save  the  acid. 

95.  Into   a  test  glass  pour  a  tablespoonful  of  sulphuric   acid,  and 
immerse  in  it  a  splinter  of  wood. 

96.  Place  5  grams  of  sugar  in  an  evaporating  dish  and  pour  10  c.  c. 
of  strong  sulphuric  acid  upon  it. 

97.  Place  27  c.  c.  of  water  in  a  beaker,  and  add  slowly  73  c.  c.  of 
concentrated  H2SC>4.     When  cool,  transfer  the  mixture  to  a  graduate, 
and  note  the  volume.     Save  the  acid. 

98.  Pour  a  few  drops  of  H2SO4  into  a  test  tube  and  dilute  with  20 
c.  fi.  of  \vater.     Add  a  little  BaCl2  solution,  and  observe  the  effect.     This 
is  the  test  for  HgSO^     (See  Expt.  90.) 

99.  Dissolve  a  crystal  of  PbN2O6  in  water  in  a  test  tube,  and  add  a 
few  drops  of  dilute  H2SC>4. 

100.  Boil   0.2   gram   flowers   of  sulphur   with    I    c.  c.  concentrated 
HNOs,  dilute  with    20  c.  c.  of  water,  and  add  a  few  drops  of  BaCla 
solution. 

EXERCISE    19.  —  PHOSPHORIC   ACID. 

101.  Dry  thoroughly  a  large  porcelain  plate,  a  small  porcelain  cap- 
sule, and  a  wide-mouthed  bottle  of  two  liters  capacity.     Put  in  the  capsule 
a  bit  of  dry  phosphorus,  of  the  weight  of  about  half  a  gram,  and  place 
the  capsule  on  the  plate;  light  the  phosphorus,  and  cover  it  at  once  with 
the  inverted  bottle.     Drop  a  little  of  the  white  powder  obtained  into  water. 
Test  the  solution  with  litmus  paper. 

102.  Touch  a  piece  of  blue  litmus  paper  to  a  piece  of  moist  phos- 
phorus. 

103.  To  10  c.  c.  of  Na2HPO4  solution  add  BaCl2  in  excess.     Filter 
the  mixture,  and  test  the  solubility  of  the  precipitate  in  ammonia  water 
and  in  dilute  chlorhydric  acid. 


104.  (I)     To  2  c.  c.  of  Na2HPO4  add  10  c.  c.  of  water,  and  2  c.  c.  of 
NH4C1,  and  i  c.  c.  of  ammonia  water.     Now  add  slowly  3  c.  c.  of  a  mixed 
solution  containing   MgSO4  and  NH4C1.     Observe  carefully  under  the 
microscope  the  character  of  the  precipitate  formed.     Filter  and  test  as 
in  103. 

105.  (II)     To  5  c.c.  of  Na2HPO4,   add  AgNO3  solution  in  slight 
excess.     Note  the  color  of  the  precipitate.     Filter  and  test  its  solubility 
in  ammonia  water,  dilute  nitric  acid  and  dilute  chlorhydric  acid.     Save 
the  silver  residues. 

106.  (Ill)     To  a  few  c.  c.   of  Na2HPO4  add   an   equal  volume  of 
a  solution  of  molybdate  of  ammonium  in  nitric  acid.     [The  last  three 
experiments  are  the  usual  tests  for  phosphoric  acid  and  phosphates.] 

107.  To  a  few  c.c.  of  Na2HPO4  add  a  few  c.  c.  of  ferric  chloride 
solution.     Now  add  ten   c.  c.  of  NaC2H3O2  solution,  and  observe  the 
effect.     Test  the  solubility  of  the  precipitate  in  HC1  and  in  HO(C2H3O). 

108.  Weigh  a  small  porcelain  dish  very  carefully.     Next  weigh  out 
15  grams  of  crystallized  sodic  phosphate  and  place  it  in  the  dish.     Heat 
carefully  over  the  burner  until  the  substance  is  reduced  to  a  white  mass, 
and  then  weigh.     Heat  again  for  a  few  moments,  and  repeat  the  weighing 
until  the  weight  of  the  dish  containing  the  substance  shows  no  further 
diminution.     Calculate  the  per  cent  of  water  that  has  been  driven  out. 
Fuse  a  little  of  the  dry  substance  on  platinum  foil  and  then  dissolve  it  in 
water  and  add  AgNO3,  and  compare  the  precipitate  with  that  obtained 
in  Expt.  105.     Ask  for  explanation.     Save  the  silver  residues. 

EXERCISE   20. — NITRIC  ACID. 

109.  Into  a  tubulated  glass-stoppered  retort  of  250  c.  c.  capacity  put 
40  grams  of  powdered  potassium  nitrate,  or,  better,  34  grams  of  powdered 
sodium  nitrate,  if  it  can  be  obtained ;  and  through  the  tubulure  pour  50 
grams  of  strong  sulphuric  acid,  which  has  been  weighed  out  in  a  bottle 
previously  counterpoised  upon  the  balance  with  shot  or  coarse  sand. 
Imbed  the  bottom  of  the  retort  in  sand  contained  in  a  small  iron  pan 
placed  over  the  gas  lamp  on  a  ring  of  the  iron  stand.     Thrust  the  neck 
of  the  retort  into  a  flask  of  from  500  to  700  c.  c.  capacity ;  the  retort  neck 
should  fit  quite  loosely  in  the  neck  of  the  flask  in  order  to  avoid  the  pos- 
sibility of  any  pressure  being  created  within  the  retort  during  the  opera- 
tion.    Place  the  flask  in  a  pan  of  cold  water,  and  cover  it  with  cloth  or 


25 

bibulous  paper,  which  must  be  kept  wet  during  the  distillation.  Heat 
the  sand  bath  moderately  (that  the  frothing  which  occurs  may  not  become 
too  violent).  When  all  frothing  has  ceased,  and  the  mass  in  the  retort  is 
in  a  state  of  tranquil  fusion,  while  very  little  liquid  passes  over  into  the 
receiver,  the  lamp  is  to  be  put  out.  Allow  the  retort  to  cool  on  the  sand 
bath,  and  do  not  attempt  to  wash  it  out. 

Transfer  the  nitric  acid  to  a  tared  beaker  and  weigh.  Put  the  acid 
into  the  bottle  prepared  for  it.  Calculate  the  amount  which  should  be 
obtained  theoretically.  Save  the  acid  for  further  experiments. 

110.  To  i  c.  c.  of  the  nitric  acid  of  Expt.  109  add  10  c.  c.  of  water. 
Touch  a  drop   of  the  mixture  to  the  tip  of  the  tongue.     Dip  a  piece  of 
blue  litmus  paper  into  the  liquid. 

111.  Dissolve  about  one  gram  of  caustic  potash  in  20  c.  c.  of  water. 
Rub  a  little  of  the  solution  between  the  fingers.     To  one  c.  c.  of  this  solu- 
tion add  20  c.  c.  of  water,  and  cautiously  taste  of  it.     Immerse  a  piece  of 
red  litmus  paper  in  it. 

112.  Into  a  flask  of  about  500  c.  c.  capacity  put  50  c.  c.  of  strong 
nitric  acid  and  5  grams  of  starch.     Warm  the  flask  gently,  and  as  soon 
as  the  mixture  begins  to  turn  reddish   brown  remove   the  lamp.     The 
experiment  must  be  performed  under  the  hood.     When  the  flask  is  cool, 
fill  it  with  water  and  empty  it  into  the  sink  under  the  hood. 

113.  Treat  a  piece  of  lead  foil  in  a  test  tube  with  HNO3,  strong  and 
dilute,  and  observe  the  result. 

114.  To  5  c.  c.  of  indigo  solution  in  a  test  tube,  add  i  c.  c.  of  HNOa 
and  warm. 

EXERCISE   21.  — NITRIC   ACID. 

[Hereafter  write  the  equations  when  possible.] 

115.  To  5  c.  c.  of  nitric  acid,  diluted  with  twice  its  bulk  of  water, 
add   cautiously   a  rather  dilute  solution  of  caustic   potash  (potassium 
hydrate,  KHO)  until  the  mixture  turns  litmus  paper  neither  red  nor  blue. 
Evaporate  the  solution  in  a  porcelain  dish,  taking  care  that  the  liquid 
does  not  actually  boil,  until  a  drop  taken  out  on  the  end  of  a  glass  rod 
becomes  nearly  solid  on  cooling.     Then  remove  the  lamp,  and  allow  the 
dish  to  become  cold.     Show  the  result,  and  learn  the  significance  of  the 
experiment. 

116.  Take  5  c.  c.  of  the  nitric  acid,  diluted  as  in  Expt.  115,  then  add  10 
grams  of  PbO.     Warm  the  mixture  and  filter  the  liquid,  while  hot,  into 


26 


another  evaporating  dish.     Evaporate  the  solution  carefully,  but  take 
away  the  lamp  when  four  fifths  of  the  liquid  have  disappeared. 

117.  Fill  a  perfectly  dry  ignition  tube  about  one  third  full  of  lead 
nitra'.e  which  has  been  finely  powdered  and  thorottghly  dried.     Connect 
the  ignition  tube  with  a  dry  bottle  and  finally  with  the  water  pan,  as 
shown  in  the  model.     The  small  bottle  must  be  surrounded  by  a  mixture 
of  ice  (or  snow)  and  salt.     Heat  the  ignition  tube  gently,  and  when  the 
evolution  of  gas  has  once  begun,  care  must  be  taken  that  the  tube  is  not 
suffered  to  cool,  so  as  to  allow  the  water  to  suck  back  from  the  water 
pan.     Red  fumes  will  fill  the    delivery  tubes,  and  will  condense  in  the 
small  bottle  to  a  brownish  yellow  liquid  if  the  experiment  is  successful. 
Test  the  gas  which  collects  at  the  water  pan. 

118.  Neutralize  I  c.  c.  of  dilute  nitric  acid  with  ammonium  hydrate, 
evaporate   to  dryness,  and  heat  a  portion  of  the  residue  gently  upon 
platinum  foil. 

EXERCISE    22.  —  OXIDES   OF   NITROGEN. 

119.  Into  a  dry  flask  of  thin  glass  of  about  300  c.  c.  capacity,  intro- 
duce  10  or  15  grams    of  ammonium  nitrate.     From   the   flask  carry  a 
delivery  tube,  No.  6,  to  the  water  pan ;  but  interrupt  the  tube  at  some 
convenient  point  to  interpose,  by  means  of  a  cork  or  caoutchouc  stopper 
with  two  holes,  a  small  bottle,  which  can  be  kept  cool  with  water.     Heat 
the  flask  moderately  and  cautiously.     When  gas  begins  to  escape  from 
the  melted  mass,  the  heat  must  be  so  controlled  that  the  evolution  of  the 
gas  shall  not  be   tumultuous.      Collect  the  gas  in  bottles   of  300  to 
400  c.  c.  capacity.     When  two  bottles  of  gas  have  been  filled,  the  delivery 
tube  may  be  withdrawn  from  the  water  and  the  lamp  extinguished. 

Insert  a  glowing  splinter  of  wood  into  a  bottle  of  the  gas. 

Burn  a  bit  of  sulphur  in  nitrous  oxide. 

Test  the  liquid  collected  in  the  interposed  bottle. 

120.  Heat  a  bit  of  ammonium  nitrate  gently  on  platinum  foil,  and 
note  the  result. 

121.  Place  15  or  20  grams  of  copper  turnings  or  filings  in  a  bottle 
arranged  precisely  as  for  generating  hydrogen,  and  pour  about  25  c.  c.  of 
dilute  nitric  acid  made  by  adding  to  the  common  strong  acid  its  own  bulk 
of  water.     Collect  three  bottles,  of  300  to  400  c.  c.  capacity,  of  the  evolved 
gas,  adding  acid  from  time  to  time  as  may  be  necessary.     Save  the  blue 
solution  (copper  nitrate)  which  remains  in  the  generator. 


27 

122.  Dip  a  lighted  candle  into  a  bottle  of  the  gas.    Into  the  same 
bottle  thrust  a  glowing  splinter. 

123.  Lift  a  bottle  of  the  gas  from  the  water  so  that  air  may  enter 
the  bottle  and  the  gas  may  escape  into  the  air.     Bring  into  contact  with 
the  fumes  a  piece  of  moistened  litmus  paper. 

124.  Thoroughly  ignite  a  bit  of  sulphur  in  a  deflagrating  spoon,  and 
introduce  it  into  a  bottle  of  the  gas.     Into  the  same  bottle  thrust  a  piece 
of  phosphorus  as  big  as  a  pea,  burning  actively. 

125.  Fill  a  test   tube  with  a  concentrated  acid  solution  of  ferrous 
sulphate.     Invert  the  tube  in  a  water  pan  over  a  delivery  tube,  from 
which  NO  is  issuing.     When  half  of  the  liquid  has  been  driven  from  the 
tube,  place  your  thumb  over  the  bottom  and  remove  the  tube  from  the 
pan  and  shake.     Boil  the  contents  of  the  tube.     Notice  all  the  changes. 


EXERCISE   23. — CARBON. 


t!26.  Put  into  an  ignition  tube  12  or  15  c.  m.  in  length,  enough 
tuminous  coal,  in  coarse  powder,  to  fill  one  third  of  the  tube.  Fit  to 
this  ignition  tube  a  large  delivery  tube,  and  support  the  apparatus  upon 
the  iron  stand,  having  the  ignition  tube  nearly  horizontal.  Heat  the 
tube  and  collect  in  bottles  the  gas  which  will  be  evolved.  Test  the  gas 
with  a  lighted  match. 

As  soon  as  gas  ceases  to  be  given  off  from  the  coal,  take  the  end  of 
the  delivery  tube  out  of  the  water,  and  when  the  ignition  tube  has 
become  cold,  break  it  and  examine  the  coke  which  it  contains. 

127.  Repeat  the  previous  experiment,  using  wood  shavings  or  saw- 
d*ust  instead  of  coal.     Collect  and  test  the  gas  evolved.     After  the  flow 
of  gas  has  ceased,  remove  the  end  of  the  delivery  tube  from  the  water, 
plug  it  so  that  no  air  can  enter  the  ignition  tube,  and  lay  the  apparatus 
aside  until  it  has  become  cold.     Finally  remove  the  cork  from  the  ignition 
tube  and  take  out  the  charcoal  which  is  contained  in  it.     Heat  a  portion 
of  this  charcoal  upon   platinum  foil   and  note  the  manner  in  which  it 
burns. 

128.  Over  a  burning  candle  invert   a  wide-mouthed  bottle   of  the 
capacity  of  a  liter  or  more,  one  edge  of  the  mouth  of  the  bottle  being 
propped  up  on  a  small  block  of  wood,  so  that  some  air  may  enter  the 
bottle.     Explain   the  formation  of  lamp-black.     Also  press  down  upon 
the  flame  of  an  oil  lamp  or  candle  an  iron  spoon  or  a  porcelain  plate  in 


such  manner  that  the  flame  shall  be  almost,  but  not  quite,  extinguished. 
Explain  the  results. 

129.  Mix  two  and  a  half  grams  of  copper  oxide  with  a  quarter  of 
a  gram  of  powdered  charcoal ;  place  a  portion  of  the  mixture  in  an  igni- 
tion tube,  and  heat  it  strongly  in  the  gas  lamp.     Test  the  gas  evolved, 
and  examine  what  is  left  in  the  tube. 

130.  Take  from  the  fire  a  piece  of  charcoal  which  has  been  heated 
to  full  redness  for  some  time  ;  thrust  it  under  water  so  that  it  may  be 
suddenly  cooled,  and  compare  its  behavior  with  that  of  a  piece  of  common 
charcoal.     Also,  attach  a  lead  sinker  to  a  piece  of  common  charcoal  and 
sink  it  in  a  beaker  of  warm  water. 

131.  Put  a  small  quantity  of  powdered  charcoal  into  a  bottle  con- 
taining hydrogen  sulphide,  close  the  bottle  tightly  with  the  palm  of  the 
hand  and  shake  for  a  few  moments.     Observe  how  much   the  odor   is 
affected ;   observe  other  attendant  phenomena. 

132.  Provide  four  small  bottles  of  the  capacity  of  100  or  200  c.  c., 
and  place  in  each  of  them  a  tablespoonf ul  of  bone-black ;  into  the  first 
bottle  pour  a  quantity  of  the  blue  compound  of  iodine  and  starch  obtained 
in  Expt.  39 ;   into  the  second,  a  decoction  of  cochineal ;  into  the  third,  a 
dilute  solution  of  soluble  indigo  blue ;  into  the  fourth,  a  solution  of  blue 
litmus,  of  logwood,  or  indeed  of  almost  any  other  vegetable   coloring 
matter;  enough  of  the  solution  being  taken  in  each  instance  to  nearly 
fill  the  bottle.     Cork  the  bottles  and  shake  them  violently,  then  pour  the 
contents  of  each  upon  a  filter  and  show  the  several  filtrates. 

133.  Mix  4  grams  of  potassium  nitrate  with  2  grams  of  powdered 
charcoal.     Place  the  mixture  upon  an  iron  plate   and   touch   it  with   a 
lighted  stick.     Perform  this  experiment  under  the  hood. 

EXERCISE   24. — CARBONIC   ACID. 

134.  Place  a  live   coal  (charcoal)  upon  a  deflagrating  spoon  and 
thrust  it  into  a  bottle  full  of  air,  or,  better,  oxygen  gas ;  when  the  coal 
has  ceased  to  glow,  pour  into  the  bottle  some  lime  water  —  a  solution  of 
common  slaked  lime  in  water  —  and  shake  the  bottle. 

135.  Mix  ii  grams  of  red  oxide  of  mercury  with  0.33  gram  of  char- 
coal ;  heat  the  mixture  in  an  ignition  tube,  and  collect  over  water  the  gas 
which  is  evolved.     Test  the  product  with  lime  water,  as  in  Expt.  134. 
Examine  what  is  left  in  the  tube. 


29 

136.  In  a  gas  bottle  of  500  or  600  c.  c.  capacity,  arranged  precisely 
as  for  generating  hydrogen,  place  10  or  12  grams  of  carbonate  of  calcium 
(marble  or  limestone).     Cover  the  end  of  the  thistle  tube  with  water  and 
then  add  strong  chlorhydric  acid  by  small  portions,  in  such  quantity  as 
shall  insure  a  continuous  and  equable  evolution  of  gas.     Collect  several 
bottles  of  the  gas  over  water,  then  replace  the  anterior  portion  of  the 
delivery  tube  with  a  straight  tube  and  collect  one  or  two  bottles  of  the  gas 
by  downward  displacement. 

137.  Thrust  into  a  bottle  of  the  gas,  obtained  in  Expt.  136,  a  lighted 
candle,  or,  better,  a  large  flame  of  alcohol  burning  upon  a  tuft  of  cotton. 

138.  From  a  large  bottle  full  of  the  gas,  pour  a  quantity  of  carbonic 
acid  upon  the  flame  of  a  lamp  or  candle ;  that  is  to  say,  hold  the  mouth 
of  the  open  bottle  of  carbonic  acid  obliquely  over  the  candle  flame,  so 
that  the  gas  shall  fall  like  water  upon  it. 

139.  Take  a  beaker  of  about  300  c.  c.  capacity  and  balance  it,  very 
carefully,  upon  the  pan  of  a  balance.     Fill  a  large  dry  bottle  with  CC»2 
and  pour  it  into  the  beaker.     Notice  the  increase  of  weight. 

140.  Into  a  long-necked  flask  or  phial  filled  with  carbonic  acid, 
pour  a  quantity  of  water,  close  the  bottle  with  the  finger,  and  shake  it; 
immerse  the  mouth  of  the  bottle  in  water  and  remove  the  finger ;  water 
will  rush  into  the  bottle  to  supply  the  place  of  the  gas  which  has  been 
dissolved.     Again  place  the  finger  upon  the  mouth  of  the  bottle,  shake 
the  bottle  as  before,  and  subsequently  open  it  beneath  the  surface  of  the 
water,  and  so  on. 

141.  Fill  a  test  tube,  by  displacement,  with  CO2.     Pour  in  5  c.  c. 
of  a  solution  of  KOH,  place  your  thumb  over  the  end,  and  shake. 
Immerse  the  tube  in  the  water  pan  and  remove  your  thumb. 

142.  Dissolve  10  grams  of  honey  or  molasses  in  100  c.  c.  of  water; 
fill  a  large  test  tube  with  the  mixture  and  add  to  it  a  few  drops  of  bakers' 
or  brewers'  yeast ;  close  the  open  mouth  of  the  test  tube  with  the  thumb 
and  invert  it  in  a  small  saucer  or  porcelain  capsule  filled  with  the  diluted 
syrup.     Place  the  saucer  and  tube,  with  their  contents,  in  a  warm  place, 
having  a  temperature  of  about  20°  or  30°,  and  leave  them  there  during  24 
hours.     In  a  short  time  fermentation  sets  in,  and  the  sugar  of  the  syrup 
is  gradually  converted  into  alcohol  and  carbonic  acid. 

143.  Take  two  small  bottles  and  into  each  put  15  or  20  c.  c.  of  clear 
lime  water.     Through  one  of  the  bottles  force  a  stream  of  ordinary  air  5 
through  the  other  force  a  stream  of  air  from  the  lungs. 


EXERCISE   25.  —  MARSH  GAS,    ETC. 

144.  Mix  together  2  grams  of  crystallized  sodium  acetate,  4  grams  of 
caustic  soda,  and  8  grams  of  slaked  lime.     Heat  the  mixture  gently  upon 
an  iron  plate,  until  all  the  water  of  crystallization  of  the  acetate  has  been 
expelled  and  the  mass  has  become  dry  and  friable.     Charge  an  ignition 
tube  20  c.  m.  long  with  the  dry  powder,  heat  it  above  the  gas  lamp,  and 
collect  the  gas  at  the  water  pan.     Marsh  gas  is  evolved  from  the  mixture, 
at  a  temperature  below  redness,  and  a  residue  of  sodium  carbonate  is 
left  in  the  ignition  tube.     The  purpose  of  the  lime  is  to  render  the  mass 
porous  and  infusible,  or  nearly  infusible,  so  that  the  tube  may  be  heated 
equably.     Attempt  to  write  equation. 

145.  Fill  a  tall  bottle  of  at  least  one  liter  capacity  with  warm  water, 
invert  it  over  the  water  pan  and  pass  marsh  gas  into  it,  until  a  little  more 
than  one  third  of  the  water  is  displaced ;  cover  the  bottle  with  a  thick 
towel,  to  exclude  the  light,  and  then  fill  the  rest  of  the  bottle  with  chlo- 
rine.    Cork  the  bottle  tightly,  and  shake  it  vigorously,  in  order  to  mix 
the  gases  together,  keeping  the  bottle  always  covered  with  the  towel. 
Finally,  "open  the  bottle  and  apply  a  light  to  the   mixture.     After  the 
action  has  taken  place  test  the  moisture  on  the  sides  of  the  bottle. 

146.  Mix  8  grams  of  powdered  magnesium  carbonate  with  16  grams 
of  zinc  dust.     Place  the  mixture  in  an  ignition  tube,  tapping  it  so  as  to 
leave  a  passage  over  the  top  for  the  gas  which  will  be  evolved.     Heat 
strongly  on  a  furnace  lamp  and  collect  the  gas  in  the  ordinary  manner 
over  the  water  pan.     Test  the  gas. 

147.  Heat  4  grams  of  CuO  in  a  piece  of  ignition  tubing  over  a  fur- 
nace lamp  and  pass  a  stream  of  CO  over  the  hot  oxide.     Collect  the  gas 
over  water  and  test  with  a  lighted  splinter  and  with  lime  water. 

148.  Sprinkle  fine  iron  filings  into  the  flame  of  an  alcohol  lamp  or 
into  the  non-luminous  flame  of  the  gas  lamp.     Also,  rub  together  two 
pieces  of  charcoal  above  a  non- luminous  flame,  in  such   manner  that 
charcoal  powder  shall  fall  into  the  flame. 

149.  Press  down  a  piece  of  white  letter  paper,  for  an  instant,  upon 
the  flame  of  a  candle  until  it  almost  touches  the  wick,  then   quickly 
remove  the  paper  before  it  takes  fire  and  observe  how  its  upper  surface 
is  charred. 

150.  Study  the  flame  of  a  candle.     Thrust  the  phosphorus  end  of 
a  match  into  the  flame,  and  see  whether  you  can  withdraw  it  without 
lighting  the  match. 


EXERCISE   26. —  SILICON   AND   BORON. 

151.  To  a  concentrated  solution  of  water  glass  contained  in  a  small 
evaporating  dish,  add  enough  strong  chlorhydric  acid  to  make  the  solu- 
tion acid.     There  will  separate   a  thick  jelly-like   mass  of  silicic   acid 
(1148104).     Evaporate  the  contents  of  the  dish  to  dryness  on  a  water 
bath  and  then  heat  the  residue  gently  over  the  gas  lamp.     The  mass  will 
contract  in  bulk  and,  on  adding  water,  there  will   remain   undissolved 
a  fine  white  powder  of  silicic  anhydride. 

152.  Take  a  very  dilute  solution  of  water  glass  and  add  dilute  chlor- 
hydric acid  drop  by  drop  until  the  liquid  has  a  decidedly  acid  reaction. 
Compare  the  result  with  that  of  the  first  part  of  the  previous  experiment. 

153.  Into  a  perfectly  dry  matrass  put  a  small  quantity  of  a  mixture 
of  equal  quantities  of  quartz  and  powdered  fluor-spar.     Moisten  with  a 
drop  of  strong  sulphuric  acid  and  heat  in  the  flame  of  a  lamp.     Hold 
a  drop  of  water  in  a  loop  of  platinum  wire  at  the  mouth  of  the  tube. 
Show  result  and  see  blackboard  for  reactions.     This  shows  how  to  recog- 
nize silicon  in  its  compounds. 

154.  Dissolve  4  grams  of  powdered  borax  in  10  grams  of  boiling 
water,  in  a  beaker  glass  or  porcelain  capsule  of  30  or  40  c.  c.  capacity, 
and  add  to  the  solution  5  c.  c.  of  concentrated  chlorhydric  acid.     Allow 
the  solution  to  cool. 

155.  Dissolve  a  little  crystallized  boracic  acid  in  a  teaspoonful  of 
alcohol  in  a  small  porcelain  capsule.     Set  fire  to  the  alcohol  and  stir  the 
burning  solution  with  a  rod  or  agitate  it  by  jarring  the  dish.     Repeat, 
using  borax  instead  of  boracic  acid.     Now  put  3  c.  c.  of  H2SC>4  upon  a 
small  portion  of  borax;  and  then  add  3  c.  c.  of  alcohol.     Light  the  mix- 
ture and  note  the  result.     What  does  the  experiment  show  ? 

156.  In  a  clean  iron  spoon  heat  some  crystallized  boracic  acid.     The 
crystals  will  melt,  and  if  the  heat  be  continued,  the  mass  will  become 
pasty  and  will  swell  up  as  the  water  is  expelled.     After  all  the  water  has 
been  driven  off  by  strong  heat,  the  anhydride  is  left  as  a  clear,  viscous 
liquid,  from  which  long  threads  may  be  drawn  out  by  touching  to*the 
surface  of  the  liquid  the  end  of  a  stick  or  glass  rod  and  then  gently  pull- 
ing away  the  stick  with  the  matter  which  has  adhered  to  it.     Allow  the 
fused  mass  to  cool,  and  examine  its  appearance. 


EXERCISE  27. — SOLUBILITY. 

[Prepare  a  wash  bottle  and  a  couple  of  stirring  rods.     See  models.] 
Solubility  in  water. 

1.  Weigh  3  portions  of  I  gram  each  of  powdered  Na2SO4,  CaSO4, 
and  PbSO4.     Take  three  test  tubes  and  place  in  each  10  c.  c.  of  water. 
Into  one  of  the  tubes  pour  one  portion  of  Na2SO4  and  shake,  and,  if  this 
dissolves,  add  the  second,  and  if  the  second  dissolves,  add  the  third. 
Repeat  the  process  with  the  CaSO4  and  PbSO4  in  the  other  tubes.     If, 
however,  the  first  lot  fails  to  dissolve,  ascertain  whether  any  dissolves  by 
filtering  (see  Appendix,  §  15)  some  of   the   mixture  very  carefully  and 
evaporating  a  few  drops  of  the  filtrate  on  a  clean  slip  of  platinum  foil. 

Solubility  in  hot  and  cold  water. 

2.  Weigh  4  portions  of  i  gram  each  of  powdered  BaN2O6.     Place 
10  c.  c.  of  water  in  a  test  tube  and  add  one  portion  and  shake.     Note  the 
result.     Warm  slowly,  and  as  often  as  the  salt  is  entirely  dissolved  add 
a  new  portion  of  i  gram.     Finally,  bring  the  liquid  to  boiling.     What 
does  the  experiment  show  ? 

Comparison  of  solubility  in  water. 

3.  [The  salts  must  all  be  powdered  !  ]    Take  5  test  tubes  and  place  in 
each  10  c.  c.  of  water.     Into  a  test  tube  put  12  or  15  grams  of  potassium 
carbonate  (KgCOg).     Weigh  the  tube  and  contents  and  record  the  weight. 
From  this  test  tube  pour  successive  small  portions  of  K2COs  into  one  of 
the  test  tubes  containing  water  as  long  as  it  will  dissolve.     Again  weigh 
the  test  tube  and  contents.     The  loss  in  weight  will  be  the  weight  of  the 
K2CO3  dissolved  in  the  water.     Calculate  the  number  of  parts  of  the  salt 
which  have  dissolved  in  100  parts  of  water.     In  like  manner  test  the  sol- 
ubility of  KNO3,  K2SO4,  SrSO4,  and  BaSO4,  starting  with  5  grams  of  the 
first,  3  grams  of  the  second,  and  i  gram  of  the  third  and  fourth.     Bring 
the  results  of  the  experiment  into  the  form  of  a  table.     (See  blackboard.) 

4.  [For  students  who  are  doing  extra  work.]     Measure  and  pour  into 
a  fl^sk  100  c.  c.  of  water.     Insert  a  thermometer  in  the  flask  by  means 
of  a  perforated  cork  so  that  the  temperature  can  be  accurately  observed. 
Note  the  temperature.     Add  Na2SO4  in  weighed  portions  of  2  grams 
each  until  no  more  can  be  dissolved  after  thorough  shaking,  and  make 
note  of  the  amount  required.     Raise  the  temperature  by  means  of  a  lamp 
underneath  to  15°,  remove  the  lamp  and  then  add  portions  of  2  grams  of 
NaaSO4  until  you  have  determined  the  amount  soluble  at  this  tempera- 


33 


ture.  Now  raise  to  20°  and  repeat  the  operation.  Finally  raise  also  to 
25°,  30°,  35°,  40°.  Make  careful'note  of  the  amount  added  at  each  point 
and  the  total  amount  in  solution  at  each  temperature.  Plot  a  curve  of 
solubility  upon  a  piece  of  cross  section  paper  similar  to  the  example  upon 
the  blackboard.  This  curve  must  be  handed  to  the  professor  before  the 
next  exercise. 

EXERCISE  28.  —  SOLUBILITY. 

State   clearly  what  is  taught  by  each  of  the  experiments 
which  follow. 

Use  of  different  solvents. 

5.  Compare  the  solubility  of  bone  ash  in  H2O,  dilute  HC1,  and  dilute 
H2SO4. 

6.  Compare  the  solubility  of  iodine  in  water,  alcohol,  and  carbon 
disulphide.    Apply  no  heat.     In  such  cases  as  this  it  is  advisable  to  take 
exceedingly  small  quantities  of  iodine  and  drop  them  into  about  3  c.  c. 
of  the  liquid ;  and  watch  the  rapidity  with  which  the  iodine  disappears, 
and  judge  from  this  in  which  liquid  it  is  the  most  soluble. 

7.  Compare  the  solubility  of  NaCl  in  H2O,  strong  HC1  and  alcohol. 

Solubility  in  Mixtures. 

8.  Attempt  to  dissolve  I  gram  of  BaClg  in  3  c.  c.  of  strong  HC1. 
Finally  add  10  c.  c.  of  water. 

9.  Dissolve  2  grams  of  NaaSO^  in  4  c.  c.  of  water,  and  add  an  equal 
volume  of  alcohol. 

10.  Dissolve  0.5  gram   iodine  in  2  c.  c.  alcohol  and  add  5  c.  c.  of 
water. 

Neutralization  of  the  solvent. 

11.  Take  some  calcium  phosphate,  dissolve  in  warm  dilute  HC1,  and 
then  add  ammonia  to  alkaline  reaction.     Repeat  the  experiment,  using 
oxalate  of  barium. 

12.  Dissolve  a  little  AgCl  in  ammonia  water  and  add  dilute  HNOs 
to  acid  reaction. 

Absorption  and  development  of  heat. 

13.  Place  25  c.  c.  of  strong  HC1  in  a  beaker.     Note  the  temperature 
of  the  acid ;  dissolve  20  grams  of  Glauber's  salt  in  the  acid,  and  again 
note  the  temperature. 


34 


14.  Place  10  c.  c.  of  water  in  a  small  beaker.     Note  the  temperature. 
Dissolve  10  grams  of  KOH  in  the  water  and  again  note  the  temperature. 

EXERCISE   29.  —  SOLUBILITY. 
Saturation. 

15.  Heat  together  10  grams  of  alum  and  8  c.  c.  of  water,  and  allow 
to  cool.     Pour  off  the  clear  liquid  and  boil  it  for  a  few  moments,  and 
allow  to  cool  again. 

16.  Place  10  grams  of  sodic  acetate  in  a  test  tube,  add  10  c.  c.  of 
water,  and  warm  until  the  sodic  acetate  has  entirely  dissolved.     Place  a 
little  cotton-wool  in  the  mouth  of  the  tube,  set  it  aside,  and  allow  to  cool 
perfectly  without  moving.     The  liquid  should  be  clear.     Now  drop  into 
the  liquid  a  small  crystal  of  sodic  acetate  and  observe  the  effect. 

26.     See  exercise  30.     Begin  the  experiment  at  this  place. 

Solution  of  liquids. 

17.  Test  the  solubility  of  the  following  liquids  in  water:  alcohol, 
ether,  olive  oil,  glycerine,  carbon  bisulphide.     Proceed  in  each  case  as 
follows :  Take  5  c.  c.  of  water  in  a  clean  test  tube ;  pour  I  c.  c.  of  the 
liquid  to  be  tested  upon  the  water  in  the  tube.     Shake  several  times,  and 
then  observe  the  depth  of  the  liquid  layer  above  or  below  the  water,  if 
any  such  layer  there  be.     Ether  and  carbon  bisulphide  are  very  inflam- 
mable and  very  volatile,  and  must  not  be  brought  anywhere  near  a  flame. 

18.  Test  the  solubility  of  benzol  in  water  and  alcohol. 

Physical  and  chemical  solution. 

19.  Take  two  portions  of  5  grams  each  of  sal-soda.     Dissolve  one 
portion  in  10  c.  c.  of  water,  evaporate  to  dryness  slowly,  and  compare  the 
substance  obtained  with  the  original  salt  in  appearance,  crystalline  form, 
and  taste.     Dissolve  the  second  portion  in  dilute  chlorhydric  acid,  evap- 
orate and  compare. 

20.  Place  5  c.  c.  of  alcohol  in  a  test  tube  and  add  I  c.  c.  of  HC1,  and 
shake.     Drop  a  small  piece  of  fused  potassium  carbonate  into  the  tube. 
Place  5  c.  c.  of  water  in  a  test  tube  and  add  I  c.  c.  of  HC1.     Drop  a  small 
piece  of  fused  potassium  carbonate  into  this  tube.     Explain. 

2 1  •     Repeat  Expt.  20,  but  use  marble  instead,  of  potassium  carbonate. 


35 


EXERCISE   30.  — CRYSTALLIZATION. 

Crystallization  by  solution. 

22.  Put  about  0.5  gram  PbClg  into  a  test  tube  with  some  10  c.  c.  of 
water.     Boil  for  a  minute  or  two,  and  then  filter  quickly  but  carefully, 
receiving  the  filtrate  in  a  clean  test  tube  kept  warm  by  being  immersed  in 
a  beaker  of  hot  water.     When  the  liquid  has  filtered  through,  remove  the 
test  tube  from  the  hot  water  and  allow  to  cool.     Examine  the  product 
under  a  microscope. 

23.  Place  5  grams  of  oxalic  acid  in  a  test  tube,  and  add  10  c.  c.  of 
water.     Heat  until  the  acid  has  dissolved,  and  then  allow  to  cool. 

Crystallization  by  sublimation. 

24.  Heat  a  small  lump  of  benzoic  acid  gently  in  a  dry  test  tube. 
Repeat  Expts.  36  and  62. 

Crystallization  by  precipitation. 

25.  To  a  few  drops  of  concentrated  common  salt  solution  add  5  c.  c. 
of  alcohol.     Examine  the  precipitate  under  the  glass. 

Crystallization  by  solution  and  evaporation. 

26.  Place  upon  small  watch  glasses  i  c.  c.  each  of  solutions  of  potas- 
sium nitrate,  potassium  chlorate,  potassium  chromate,  mercuric  chloride, 
and  sodium  acetate,  and  allow  the  glasses  to  stand  in  your  desk  until  the 
next  exercise.     Then  observe  carefully  with  the  lens  the  forms  of  crystals 
obtained. 

Piirification  by  crystallization. 

27.  Weigh  25  grams  of  soda  ash.     Place  in  a  beaker,  and  pour  upon 
the  ash  50  c.  c.  of  water.     Heat  until  the  ash  has  dissolved,  filter  the  tur- 
bid solution  while  hot,  and  allow  to  cool.     Remove  some  of  the  crystals, 
place  in  an  evaporating  dish,  and  heat  until  they  are  reduced  to  a  fine 
powder.     Compare  this  powder  with  the  original  ash.  . 

Water  of  Crystallization. 

28.  Grind  together  in  a  mortar  4  grams  of  crystallized  sodium  sul- 
phate (Glauber's  salt)  and  2  grams  of  potassium  carbonate. 

29.  Heat  a  crystal  of  copper  sulphate  in  a  test  tube  until  no  more 
steam  passes  off.    Also  repeat  Expt.  9.     What  is  taught  ?     Heat  a  crystal 
of  common  salt  in  a  test  tube.     How  does  it  differ  from  the  former  case  ? 
Why? 


EXERCISE   31.  — SODIUM   AND   AMMONIUM    SALTS. 

157.  Cover  the  bottom  of  a  large  bottle  (at  least  a  liter  bottle)  with 
hot  water,  drop  in  a  piece  of  sodium  as  large  as  a  small  pea,  and  imme- 
diately cover  the  mouth  of  the  bottle  with  a  card  or  glass  plate.     Test 
the  liquid  with  litmus  paper.     Also  perform  the  experiment  using  cold 
water. 

158.  Place  a  bit  of  sodium  upon  charcoal,  and  ignite  by  means  of 
the  blow-pipe. 

159.  Wrap  a  bit  of  sodium  in  tissue  paper  and  lay  it  upon  a  piece  of 
ice. 

160.  Place  in  a  test  tube  5  c.  c.  of  concentrated  NaOH,  and  add 
slowly  5  c.  c.  of  strong  HC1.     Write  the  equation. 

161.  Weigh  out  exactly  9  grams  of  fine  salt,  and  add  it  to  25  c.  c. 
(measured)  of  water  at  the  ordinary  temperature.     Shake  until  the  salt 
has  dissolved,  then  add  another  gram.     If  this  fails  to  dissolve,  bring  the 
mixture  to  boiling.     If  all  dissolves,  show  the  solution. 

162.  Heat  a  crystal  of  NaCl  upon  platinum  foil.     State  what  action 
takes  place  and  why.    Observe  the  color  of  the  flame  due  to  the  presence 
of  sodium. 

163.  Mix  i  gram  of  powdered  anhydrous  Na2SC>4  with  an   equal 
weight  of  powdered  charcoal.     Add  a  few  drops  of  water  and  make  a 
paste.     Heat  a  portion  of  this  paste  before  the  blow-pipe  on  charcoal 
as  strongly  as  possible.     The  Na2SO4  will  be  reduced  to  Na2S.    Treat 
a  piece  of  the  fused  mass  with  dilute  HC1.    Also  place  a  bit  upon  a 
silver  coin  and  moisten  with  a  drop  of  water. 

164.  Soda  by  lime.     Dissolve  15  grams  of  crystallized   sal-soda  in 
60  c.  c.  of  water.     Mix  4  grams  of  slaked  lime  with  15  c.  c.  of  water. 
Heat  the  solution  of  sal-soda  in  an  iron  dish  nearly  to  boiling,  and  add 
slowly  the  milk  of  lime,  and  boil  for  a  few  moments. 

Na2CO3  +  CaH2O2  =  2  NaHO  -f  CaCO3. 

By  decantation  and  evaporation  the  liquor  obtained  will  yield  NaOH. 
Pour  the  liquid  from  the  iron  dish  into  a  beaker,  allow  to  settle,  decant 
a  portion  of  the  clear  liquor  back  into  the  iron  dish,  and  evaporate  until 
the  NaOH  separates. 

165.  To  a  few  cubic  centimeters  of  a  solution  of  ammonium  chloride 


37 

in  a  test  tube,  add  a  few  drops  of  a  solution  of  caustic  soda,  and  boil  the 
liquid.     Observe  the  odor. 

What  similar  experiment  has  already  been  performed  ? 

166.  Place  a  bit  of  sal-ammoniac  in  the  bottom  of  a  dry  test  tube 
and  heat  it  slowly.     Place  bits  of  litmus  paper  at  different  positions  in 
the  test  tube,  and  notice  the  action.     Ask  for  explanation. 

EXERCISE   32.  —  AMMONIUM    SALTS   AND   POTASSIUM. 

[Those  who  did  not  perform  experiments  165  and  166  will  do  so  before 
proceeding.] 

167.  Mix  thoroughly  5  grams  of  NH^Cl  and  10  grams  of  CaCOs  by 
grinding  in  a  mortar,  and  heat  in  a  small  evaporating  dish  upon  a  sand 
bath  under  the  hood.     As  soon  as  white  fumes  begin  to  rise  place  a  large 
dry  bottle  or  funnel  over  the  dish  and  collect  the  white  sublimate.    Test 
this  for  a  carbonate. 


While  the  experiment  is  going  on  proceed  with  other  experiments. 

168.  Place  100  grains  of  wood  ashes  on  a  filter  and  pour  hot  water 
over  them,  collecting  the  filtrate  in  a  bottle  and  returning  it  upon  the 
ashes  two  or  three  times,  in  order  to  obtain  a  strong  solution.     To  exhaust 
the  ashes  of  their  potash  they  must,  of  course,  be  treated  with  successive 
portions  of   hot  water.     Test  the  solution  with  litmus  paper  and  then 
evaporate  it  to  dryness  while  succeeding  experiments  are  being  per- 
formed.    Finally  weigh  the  residue  obtained  and  calculate  the  per  cent 
of  soluble  matter  in  the  ash.     Treat  the   residue  with  HC1  after  the 
weight  has  been  recorded. 

169.  Heat  in  a  dry  test  tube  strongly  3  grams  of  potassium  tartrate. 
When  the  tube  has  become  cool  pour  in  boiling  water,  shake  and  filter. 
Add  acid  to  the  filtrate  and  notice  that  CO2  is  given  off.     This  illustrates 
the  formation  of  K2CO8  in  the  ashes. 

170.  Throw  a  piece  of  potassium,  as   large  as  a  small   pea,  upon 
some  cold  water  in  the  bottom  of  a  large  bottle,  and  place  a  card  or  glass 
plate  over  the  mouth  of  the  bottle.     Test  the  liquid  with  litmus  paper. 

171.  To  a  gas  bottle  in  which  carbonic  acid  is  being  steadily  evolved 
according  to  Expt.  136,  attach  a  chloride  of  calcium  tube,  and  beyond 


38 

this  drying  tube  a  short  tube  of  hard  glass,  from  which  an  exit  tube  leads 
into  a  small  open  bottle.  When  the  extinction  of  a  lighted  match  in 
the  open  bottle  proves  the  apparatus  to  be  full  of  carbonic  acid,  thrust 
into  the  hard  glass  tube  a  bit  of  potassium  as  big  as  a  pea,  previously 
dried  between  folds  of  blotting  paper;  then  gently  heat  the  potassium 
with  a  lamp.  When  the  tube  has  become  cold,  place  it  in  a  tube  or 
bottle  of  water,  filter  the  solution,  note  the  appearance  of  the  particles 
in  the  filter,  evaporate  the  filtrate  to  dryness,  add  a  few  drops  of  dilute 
HC1. 

172.  Test  for  potassium.     I.  Dip  a  platinum  wire  in  a  solution  of 
KC1,  and  place  the  wire  in  the  flame  of  a  Bunsen  burner.     2.  To  I  c.  c. 
of  a  solution   of  KC1   add  i  drop   of   PtCl4.     3.  Place    in   a  test  tube 
3  c.  c.  of  KC1  solution,  add  an  equal  volume  of  a  solution  of  tartaric  acid, 
and  shake. 

EXERCISE   33. — BARIUM,   CALCIUM,   AND   STRONTIUM. 

At  this  exercise  each  student  will  have  an  opportunity  to  examine  the 
spectroscope. 

173.  By  means  of  iron  wire,  suspend  three  small  bullets  of  well- 
burned  coke  from  a  ring  of  the  iron  stand.     Heat  the  fragments  in  turn 
with  the  flame  of  the  gas  lamp,  and  observe  the  slightly  yellowish  flame 
which  will  be  produced  in  each  case ;  then  moisten  one  of  the  pieces  of 
coke  with  a  solution  of  calcium  chloride,  the  second  with  a  solution  of 
barium  nitrate,  the  third  with  a  solution  of  strontium  nitrate,  and  again 
heat  them  in  turn  with  the  gas  flame  and  observe   the   colors  of  the 
flames. 

174.  Mix  carefully  3  grams  of  powdered  KC1O3,  5  grams  of  dry 
SrN2O6  and  2  grams  of  flowers  of  sulphur.     Place  the  mixture  upon  an 
iron  plate  and  ignite  under  the  hood. 

175.  Repeat  Expt.  174  but  use  3  grams  KC1O3,  5  grams  BaN2O6, 
i  gram  of  sulphur,  and  0.5  gram  powdered  charcoal. 

176.  Pour  a  few  drops  of  BaH2O2  solution   upon  a  watch  glass. 
Notice  how  quickly  it  absorbs  CO2  from  the  air. 

177.  Prepare  a  solution  of  "  bicarbonate  "  of  calcium  by  passing  CO2 
into  lime  water  (dilute)  until   clear.     Boil  a  part  of  the  solution   and 
observe;  to  another  portion  add  Na2CO3  solution,  and  observe. 


39 

178.  Mix  together  5  c.  c.  of  a  concentrated  solution  of  CaClg  and 
5  c.  c.  of  a  saturated  solution  of  Na2SO4.     Examine  the  precipitate  under 
the  microscope.    Write  the  equation. 

179.  Place  a  small  piece  of  CaCl2  upon  a  watch  glass.    Notice  its 
condition  at  the  end  of  the  exercise.    Illustrates  deliquescence. 

180.  Into  each  of  two  test  tubes  of  equal  size  put  the  same  amount, 
say  six  drops  (not  more),  of  a  CaCl2  solution,  marked  "  For  Expt.  180." 
Into  one  of  the  tubes  put  1 5  c.  c.  of  NH4C1  solution,  into  the  other  put 
1 5  c.  c.  of  water.    Then  add  an  equal  quantity,  say  5  c.  c.  of  carbonate  of 
ammonium  to  each.     Show  the  result. 

181.  Fill  an  ignition  tube  one  third  full  of  bleaching  powder,  and 
arrange  the  apparatus  so  that  any  gas  which  is  evolved  may  be  collected 
over  water.     Heat  the  tube  and  test  the  gas  collected 


EXERCISE   34.  —  MAGNESIUM,   CADMIUM   AND  ZINC. 

182.  Pour  5  c.  c.  of  MgSO4  solution  into  each  of  two  test  tubes. 
To  the  first  add  a  few  drops  NH4OH,  to  the  second  add  5  c.  c.  NH4C1 
and  then  a  few  drops  of  NH4OH.     Repeat  the  experiment,  but  use 
(NH4)2CO3  instead  of  NH4OH.     Explain. 

183.  Place  3  c.  c.  of  MgSO4  solution  in   a  test  tube.     Add  5  c.  c. 
NH4C1  and  5  c.  c.  NH4OH.     Dilute  with  an  equal  volume  of  water,  add 
3  c.  c.  Na2HPO4  solution  and  allow  to  stand.     The  crystalline  precipitate 
thus  obtained  is  the  test  for  magnesium. 

184.  Take  10  c.  c.  of  cadmium  sulphate  solution  in  a  beaker,  and 
dilute  with  20  c.  c.  of  water  and  add  a  few  drops  of  HC1.     Saturate  with 
H^S.     Observe  the  appearance  of  the  precipitate.     Test  its  solubility  in 
dilute  HC1  and  dilute  H2SO4,  also  in  NaHS. 

185..  Place  a  bit  of  zinc  in  each  of  three  test  tubes.  To  the  first  add 
dilute  HNO3,  to  the  second  dilute  HC1,  and  to  the  third  dilute  H2SO4, 
and  warm. 

186.  Place    in    a    test    tube    2   grams   of    zinc  dust;  pour  upon  it 
5  c.  c.  of  caustic  soda  solution,  and  warm  the  mixture.     Explain  the 
results. 

187.  Place  5  c.  c.  of  zinc  sulphate  solution  in  a  test  tube,  and  add 
to  it  caustic  soda  solution  in  small  quantity  —  say  three  or  four  drops. 
Finally  add  a  larger  quantity  —  say  3  c.  c.     Explain  the  results. 

188.  Immerse  a  piece  of  zinc  in  a  solution  of  copper  sulphate. 


189.  Place  in  each  of  two  test  tubes  5  c.  c.  of  ZnSO4  solution,  dilute 
with  an  equal  volume  of  water,  and  to  one  add  i  c.  c.  of  dilute  HCl  and 
to  the  other  i  c.  c.  of  acetic  acid.  Now  saturate  both  tubes  with  H2S 
and  state  what  happens  and  why. 

190-  Heat  2  grams  of  ZnO  in  a  dry  test  tube  nearly  to  redness  and 
observe  the  color.  Allow  to  cool  and  notice  again. 

EXERCISE  35.  —  MERCURY. 

191.  Examine  the  action  o£  dilute  acids  upon  mercury  as  usual,  but 
use  a  very  small  quantity  of  the  metal. 

192.  To  a  solution  of  mercuric  chloride  add  a  solution  of  caustic 
soda  as  long  as  a  precipitate  falls. 

HgCl2  +  2  NaHO  =  HgO  +  2  NaCl  +  H2O. 

193.  To  a  solution  of  mercurous  nitrate,  add  in  the  same  way  a  solu- 
tion of  caustic  soda. 

Hg2N2O6  -}-  2  NaHO  =  Hg2O  +  2  NaNO3  -f-  H2O. 

194.  Take  10  c.  c.  of  HgCl2  solution,  dilute  with  20  c.  c.  of  H2O, 
heat   to  boiling,  and   pass  in  H2S  to   saturation,  meanwhile  observing 
changes  in  color.     Filter,  and  test  the  solubility  of  the  HgS  in  HCl, 
HNOs,  and  aqua  regia. 

195.  Take  two  test  tubes.     Place  in  one  5  c.  c.  of  Hg2N2Oe,  and  in 
the  other  5  c.  c.  of  HgN2Oe.     Add  HCl  slowly,  and  notice  the  difference 
in  the  result.     Explain. 

196.  Compare  the  solubility  in  hot  and  cold  water  of  HgCl2   and 
Hg2Cl2. 

197.  To  a  solution  of  albumin  add  a  few  drops  of  corrosive  subli- 
mate.    See  §  497,  p.  279  of  Eliot  and  Storer's  Manual. 

198.  Make  a  solution  of  ammonia  to  contain  i  part  NHs  by  weight 
in  500,000  parts  of  water.     See  blackboard.     Take  two  test  tubes  of 
equal  diameter  and  place  in  one  25  c.  c.  of  the  dilute  ammonia  and  in  the 
other  25  c.  c.  of  distilled  water.     Add  a  few  drops  of  Nessler's  solution 
(a  solution  of  HgI2  in  KI  and  KOH)  to  each  tube  and  allow  to  stand  for 
five  minutes.     Notice  the  strong  yellow  color  imparted  to  the  solution 
containing  the  NHs.     This  is  the  best  test  for  NH3  when  present  in 
minute  quantities. 

199.  Take  5  c.  c.  of  HgCl2  solution  and  add  10  drops  of  KI.     Filter 
the  precipitate  and  dry.     Into  a  clean  and  perfectly  dry  test  tube  put  a 


small  amount  of  the  HgI2.  Warm  the  middle  portion  of  the  tube  until 
you  cannot  quite  bear  your  hand  upon  it;  then  heat  rather  gently  the 
lower  part  of  the  tube  where  the  HgI2  is.  Explain. 

EXERCISE  36.  —  COPPER. 

200.  Examine  the  action  of  dilute  acids  upon  copper  in  the  usual 
manner. 

201.  Mix  equal  weights  of  powdered  CuCl2  and  Na2CO3,  and  reduce 
upon  charcoal. 

202.  Bind  a  bright  copper   coin  with  wire,  in  such  manner  that  a 
strip  of  wire  8  or  10  c.  m.  long  shall  be  left  projecting  from  the  coin; 
thrust  the  free  end  of  the  wire  into  a  long  cork  or  bit  of  wood,  and  by 
means  of  this  handle  hold  the  coin  obliquely  in  a  small  flame  of  the  gas 
lamp.      Thrust  the  hot  coin  into  water,  and   observe  that  it  is  at  this 
stage  covered  with  a  red  coating  of  copper  suboxide.     Replace  the  coin 
in  the  lamp  and  hold  it  in  the  hot  oxidizing  portion  of  the  flame ;  it  will 
soon  become  black  from  the  formation  of   copper   protoxide.     After  a 
rather  thick  coating  of  oxide  has  been  formed,  again  quench  the  coin  in 
water.     Note  what  happens. 

203.  Dissolve  a  gram  of  copper  in  as  small  a  quantity  as  possible  of 
HNOs  diluted  with  an  equal  bulk  of  water.     Evaporate  the  solution  to 
dryness;  and  finally  ignite  the  residue  until  red  fumes  are  no  longer 
given  off. 

204.  Place  in  a  test  tube,  or  small  bottle,  8  or  10  c.  c.  of  a  cold 
dilute  solution  of  copper  sulphate,  and  add  to  it  enough  of  a  solution  of 
caustic  soda  to  render  the  mixture  alkaline  to  test  paper. 

205.  Repeat  Expt.  204,  with   the  difference  that  the  solutions  of 
caustic  soda  and  copper  sulphate  are  both  heated  to  boiling,  and  are 
mixed  while  hot. 

206.  Again  repeat  Expt.  204,  but  instead  of  soda  lye  add  to  the 
copper  salt  ammonia  water,  drop  by  drop,  and  shake  the  tube  after  each 
addition  of  the  ammonia. 

207.  To  a  cold  dilute  solution  of  copper  sulphate  add  a  few  drops 
of  a  solution  of  grape  sugar ;  then  add  enough  caustic  potash  solution  to 
dissolve  the  precipitate  which  forms  at  first.     Warm  the  mixture  ;  a  yel- 
lowish precipitate  of  cuprous  hydrate  forms  in  the  liquid,  and  by  further 
heating  is  converted  into  the  red  cuprous  oxide.    Other  reducing  agents, 


42 


such  as  arsenious  acid,  for  example,  may  be  substituted  for  the  grape 
sugar. 

208.  Acidify  10  c.  c.  of  copper  sulphate  solution  with  acetic  acid. 
Add  a  few  drops  of  potassium  ferrocyanide.    This  test  for  copper  is  even 
more  delicate  than  the  one  given  in  Expt.  206. 

209.  Take  10  c.  c.  of  CuSO4  solution  and  saturate  with  H2S.     Fil- 
ter and  examine  the  solubility  of  the  CuS  in  HC1,  HNO3  and  Na2Sx. 

210.  Prepare  a  little  moist  CuS,  collect  on  a  filter  and  leave  for  a 
day  or  two.     Then  put  paper  and  all  into  a  test  tube,  shake  up  with  say 
10  c.  c.  of  water,  let  stand  for  a  few  minutes,  filter,  and  add  ammonia 
water  to  the  filtrate.    Explain  the  results  obtained. 


EXERCISE   37.  —  SILVER. 

[Finish  Expt.  210  if  you  began  it.] 

211.  Place  one  or  two  dimes  in  a  small  flask,  and  cover  them  with 
nitric  acid  diluted  with  twice  its  bulk  of  water.     Warm  the  flask  gently 
in  a  place  where  there  is  a  good  draught  of  air ;  add  more  nitric  acid, 
from  time  to  time,  if  necessary  to  complete  the  solution,  but  carefully 
avoid  having  a  great  excess  of  the  acid.     Note  the  character  of  the 
evolved  fumes  and  the  color  of  the  solution.     Dilute  the  solution  with  an 
equal  volume  of  water,  place  in  it  two  or  three  copper  coins  and  leave 
until  the  next  exercise.     Then  collect  the  little  plates  of  pure  silver, 
which  have  separated  from  the  solution,  upon  a  filter,  and  wash  them, 
first  with  water,  and  then  with  ammonia  water,  until  the  ammonia  water 
no   longer   shows   any  tinge  of  blue.     This   silver  washed   finally  with 
water  and  dried,  is  well-nigh  pure;  if  it  be  again  dissolved  in  nitric  acid, 
the  solution  will  contain  nearly  pure  silver  nitrate. 

212.  Fill  three  test  tubes  one  third  full  of  water,  and  pour  into  each 
a  few  drops  of  a  moderately  strong  solution  of  silver  nitrate.     Add  to 
the  first  test  tube  2  or  3  c.  c.  of  a  solution  of  sodium  chloride,  to  the  sec- 
ond tube  2  or  3  c.  c.  of  a  solution  of  potassium  bromide,  and  to  the  third 
tube  I  or  2  c.  c.  of  a  solution  of  potassium  iodide ;  shake  the  mixture  in 
each  case  and  describe  the  precipitates.* 

Withdraw  from  each  test  tube  a  portion  of  the  precipitate  it  contains, 
and  try  to  dissolve  each  precipitate  in  dilute  nitric  acid. 

*  Save  all  the  silver  residues. 


43 

Withdraw  from  each  test  tube  another  portion  of  the  precipitate  it 
contains,  and  treat  each  precipitate  with  ammonia  water.  Lastly,  pour 
upon  the  remnants  of  the  original  precipitates  in  the  three  test  tubes  a 
solution  of  sodium  hyposulphite. 

213.  Precipitate  some  curdy  silver  chloride  by  adding  sodium  chlo- 
ride solution,  or  chlorhydric  acid,  to  a  solution  of  silver  nitrate,  so  long 
as  any  precipitate  is  produced.     Throw  the  precipitate  upon  a  filter,  and 
wash  it  with  water ;  then  open  the  filter,  spread  the  chloride  evenly  over 
it,  and  place  it  in  direct  sunlight.* 

214.  (i)     To  a  solution  of  AgNO&  add   NaOH.     (2)     Pass  H2S 
through  a  solution  of  AgNOs.     (3)     Take  three  test  tubes  and  place 
2  c.  c.  of  AgNOg  solution   in  each.     To  the   first  add  a  few  drops  of 
Na2HPC>4,  to  the  second  a  few  drops  of  Na2CC>3,  and  to  the  third  a  few 
drops  of  K2CrO4.     Write  the  reactions.* 

215.  Precipitate  AgCl  as  in  Expt.  213,  filter,  dry  and  mix  a  portion 
or  the  whole  with  four  times  its  bulk  of  carbonate  of  sodium  and  reduce 
upon  charcoal.* 

EXERCISE   38. — ALUMINUM. 

216.  Place  a  piece  of  aluminum  in  each  of  three  test  tubes  and 
examine  the  action  of  acids  upon  the  metal  as  in  Expt.  185. 

217.  Precipitate   a  considerable    quantity  of    A12H6O6   and    filter. 
Place  two  thirds  of  the   precipitate  in  a  small   porcelain  dish  and  dry 
slowly  over  the  lamp.     Finally,  when  steam  is  no  longer  given  off,  heat 
strongly  and  observe  the  properties  of  the  residue.     Compare  the  solu- 
bility of  the  original  precipitate  and  of  the  residue  in  HC1. 

Al2H606  =  Al2O3  +  3  H2O. 

218.  Ignite  a  small  quantity  of  A12H6O6  before  the  blow- pipe  upon 
charcoal.     Moisten  the  white  powder  so  obtained  with  CoN2O6  and  con- 
tinue the  heating.     Notice  the  blue  color  obtained.     This  is  a  test  for 
aluminum. 

219.  Take  a  small  quantity  of  a  solution  of  cochineal,  add  to  it  an 
equal  bulk  of  a  solution  of  aluminum  sulphate  (or  of  common  alum),  and 
then  add  to  the  mixture  ammonia  water.     A   colored  precipitate,  consist- 
ing of  aluminum  hydrate  and  of  the  coloring  matter  of  the  cochineal, 
will  be  thrown  down ;  it  is  the  substance  called  carmine  lake. 

*  Save  all  the  silver  residues. 


44 


220.  Prepare  an  acetate  of  aluminum  solution  as  follows  :  Dissolve 
6  grams  of  sugar  of  lead  (lead  acetate)  in  8  c.  c.  of   hot  water;    also 
dissolve  8  grams  of  common  alum  in  12  c.  c.  of  hot  water;  mix  the  two 
solutions  and  filter  off  the  insoluble  lead  sulphate  which  is  formed.     In 
the  solution  thus  prepared,  soak  a  piece  of  cotton  cloth,  and  then  dry 
it.     Treat  this  cloth,  as  well  as  a  piece  of  ordinary  cotton  of  the  same 
size,  with   a   solution   of  logwood,  and    observe   the    difference   in   the 
amount  of  color  imparted  to  the  fabric. 

221.  Place  a  considerable  quantity  of  powdered  aluminum  sulphate 
in  a  test  tube,  add  10  c.  c.  of  water  and  shake  until  a  saturated  solution 
is  obtained.     Take  a  second  test  tube  and  obtain  a  saturated  solution  of 
powdered  K^SO-*.     Now  in  a  third  test  tube  mix  5  c.  c.  each  of  these 
saturated  solutions      Shake   and   observe   the   precipitate.     Filter   and 
examine  the  precipitate  under  the  microscope  and  test  its  solubility  in 
I^O.     Examine  a  piece  of  aluminum. 

EXERCISE   39.  —  TIN,   GOLD,   AND   PLATINUM. 

222.  Heat  a  piece  of  common  tinned  iron  over  the  gas  lamp  until 
the  tin  has  melted,  thrust  the  plate  into  cold  water  in  order  that  the  tin 
may  harden  quickly,  then  remove  the  smooth  surface  of  the  metal  by 
rubbing  it  first  with  a  bit  of  paper  moistened  with  dilute  aqua  regia,  and 
then  with  paper  wet  with  soda  lye.     Show  the  result. 

223.  Pour  20  c.  c.  of  SnClg  solution  into  a  beaker  and  then  pour 
an  equal  volume  of  water  upon  it,  but  do  not  allow  the  two  layers  of 
liquid  to  mix.     Thrust  a  slip  of  zinc  through  the  liquid  and  observe 
what  happens. 

224.  Examine  the  action  of  HC1,  HNO3  and  H2SO4  upon  metallic 
tin,  both  in  dilute  and  concentrated  state. 

225.  Dry  some   of  the  white   powder   obtained   by  the   action   of 
HNOg  on  tin,  mix  it  with  2  or  3  times  its  bulk  of  powdered  "binoxalate 
of  potash  "  and  endeavor  to  reduce  upon  charcoal. 

228.  Take  two  test  tubes  and  place  in  each  i  c.  c.  of  SnCl2  solution. 
Dilute  with  10  c.  c.  of  water.  To  one  of  the  tubes  add  potassium  per- 
manganate until  a  faint  color  is  obtained.  Now  saturate  both  tubes  with 
H2S.  Explain.  Test  the  solubility  of  the  precipitates  in  HC1,  concen- 
trated and  dilute,  and  Na2S.  Explain. 

227.  Take  I  c.  c.  of  SnCls  solution  and  dilute  with  10  c.  c.  of  water. 
Add  a  few  drops  of  HgCl2.  Give  equation. 


45 

228.  Place  two  drops  of  AuCls  in  a  beaker  and  dilute  with  20  c.  c.  of 
water.     To  a  few  c.  c.  of  SnCl2  solution  in  a  test  tube  add  a  few  drops 
of  Fe^Cls  and  then  add  a  few  drops  of  this  mixture  to  the  water  contain- 
ing AuClg.     Notice  the  coloration  due  to  the  formation  of  "purple  of 
Cassius."    This  is  the  most  delicate  test  for  gold. 

229.  Pour  3  c.  c.  of  a  solution  of  ammonium   chloride  into  a  test 
tube,  acidulate  the  liquid  with  chlorhydric  acid,  and  add  to  it  a  drop  of 
the  solution  of  platinum  chloride,  and  examine  the  precipitate  under  the 
microscope.    Repeat  the  experiment,  and  this  time  take  enough  of  the 
platinum  solution  and  of  the  ammonium  chloride  to  make  half  a  teaspoon- 
ful  of  the  yellow  precipitate,  taking  care  that  at  last  there  shall  be  a  slight 
excess  of  free  ammonium  chloride  rather  than  of  platinum  chloride  in 
the  supernatant  liquid.     Allow  the  precipitate  to  settle,  separate  it  from 
the   clear  liquor  by  decantation,  and  dry  it  partially  at  a  gentle  heat. 
When  the  precipitate  has  acquired  the  consistence  of  slightly  moistened 
earth,  transfer  it  to  a  cup-shaped  piece  of  platinum  foil,  and  heat  it  to 
redness  in  the  gas  flame,  as  long  as  fumes  of  ammonium  chloride  con- 
tinue to  escape.     All  the  chlorine,  hydrogen  and  nitrogen  will  be  driven 
off,  and  there  will  remain  upon  the  foil  a  gray,  loosely  coherent,  sponge- 
like  mass  of  metallic  platinum  ;  it  is  called  platinum  sponge. 

230.  Hold   the  dry  platinum   sponge  of   Expt.  229  in  a  stream  of 
hydrogen  or  of  common  illuminating  gas  issuing  from  a  fine  jet. 

EXERCISE   40.  —  LEAD. 

231.  Heat  a  small  fragment  of  lead  upon  charcoal  in  the  oxidizing 
flame  of  the  blow-pipe. 

232.  Fill  a  small  ignition   tube   one  fourth  full   of  lead   tartrate. 
Heat  the  tube  gently  until  no  more  fumes  are  given  off.     Metallic  lead 
will  be  left  in  the  tube  in  a  very  finely  divided  condition.     Cork  tightly 
while  hot  and  allow  to  become  perfectly  cold,  then  pour  some  of  the 
powder  into  an  evaporating  dish,  holding  the  tube  high  over  the  dish. 
Observe  what  happens. 

233.  Place  a  small  piece  of  lead  in  each  of  three  test  tubes.     Pour 
a  few  c.  c.  of  dilute  HNOs  upon  the  first,  a  few  c.  c.  of  dilute  HC1  upon 
the  second,  and  a  few  c.  c.  of  dilute  H2SC>4  upon  the  third.     Warm  and 
observe  the  action. 

234.  Mix  equal  bulks  of  litharge  and  sodic  carbonate  and  reduce 
upon  charcoal. 


46 

235.  Dissolve  0.5  gram  lead  acetate  in  i  liter  of  water.     Take  loo 
c.  c.  of  this  solution  and  dilute  with  about  a  liter  of  water ;  then  take  a 
small  portion  of  this  solution  and  pass  H2S  through  it.     This  is  a  most 
delicate  test  for  Pb. 

236.  To  .a  solution  of  PbN2O6  add  HC1  until  no  further  precipitate 
is  formed.     Write  the  equation.     Filter  off  the  precipitate,  and  to  one 
third  of  the  filtrate  add  dilute  H2SO4;  to  another  third,  add  H2S  water; 
to  the  remainder,  add  K2CrO4  solution.    Write  equations.     Dissolve  the 
original  precipitate  in  the  least  possible  quantity  of  boiling  water,  filter 
and  allow  to  cool. 


EXERCISE   41. — CHROMIUM  AND  MANGANESE. 

237.  Weigh  out  2  grams  of  chromic  oxide,  4  grams  of  sodic  car- 
bonate and  2  grams  of  potassic  nitrate.     Mix  thoroughly  and  fuse  in  an 
iron  ladle  until  no  more  black  specks  are  to  be  seen  in  the  fused  mass. 
Pour  out  the  fused  mass  upon  a  broken  piece  of  porcelain,  allow  to  cool 
and  break  into  small  pieces.     The  fusion  oxidized  the  chromium  to  the 
condition  of  chromic  acid.     The  fused  mass  contains  sodic  chromate. 
Dissolve  in  water  and  add  to  a  portion  of  the  solution  acetic  acid  to  acid 
reaction  and  then  acetate  of  lead.     Acidify  likewise  two  other  portions, 
and  to  one  add  ZnCl2  and  to  the  other  BaCl2. 

238.  To  10  c.  c.  of  chrome  alum  solution  add  NH-iOH  in  excess. 
Filter  the  precipitate  and  ignite  a  portion  in  a  porcelain  crucible.     Test 
the  solubility  of  the  original  and  of  the  ignited  precipitate  in  HC1. 

239.  Place  20  c.  c.  of  a  saturated  solution  of  bichromate  of  potas- 
sium  in  a  beaker  surrounded   by  cold  water.     Add   slowly  25  c.  c.  of 
strong  H2SC>4.     Observe  the  deposition  of  chromic  anhydride.     Remove 
some  of  the  crystals  and  test  their  solubility  in  water. 

240.  To  a  solution  of  MnCl2  or  MnSO4  add  NHJIS.     Collect  the 
precipitate  on  a  filter  and  allow  to  remain  exposed  to  the  air  for  some 
time. 

241.  Fuse  together  upon  platinum  foil  0.5  gram  dry  Na^COs,  o.i 
gram  KNO3  and  a  few  milligrams  of  MnO2.     The  color  given  to  the 
fused  mass  is  one  of  the  best  tests  for  manganese. 

242.  Place  in  a  test  tube   10  c.  c.   of  dilute  HNOs  and  0.5  gram 
PbO2.     Add  a  few  milligrams  of  MnO2  and  boil.     Allow  to  settle  and 
observe ;  ask  for  an  explanation  of  what  you  have  observed. 


47 

243.  In  a  beaker  or  flask  dissolve  0.25  gram  of  crystallized  oxalic 
acid  in  50  c.  c.  of  water,  add  5  c.  c.  strong  sulphuric  acid,  and  warm  the 
solution  to  about  60°.     Then  add  a  solution  of  potassium  permanganate 
tlrop  by  drop,  and  observe  that  the  color  is  at  first  immediately  destroyed. 
Continue  to  add  the  permanganate  until  it  is  no  longer  decolorized.     The 
reaction  that  has  taken  place  may  be  thus  represented : 

K2Mn2O8  +  5  C2H2O4  +  3  H2SO4  = 
2  MnS04-fK2SO4  +  8  H2O-J-10  CO2. 

The  oxalic  acid  (C2H2O4)  is  entirely  converted  into  water  and  carbonic 
acid  :  the  potassium  permanganate  gives  up  its  oxygen  and  is  converted 
into  a  mixture  of  manganese  and  potassium  sulphates. 

244.  Mix  together  in  an  iron  ladle  5  grams  KOH,  3.5  grams  pow- 
dered KClOg,  4  grams  powdered  MnO2  and  10  c.  c.  water.     Evaporate  to 
dryness  rapidly  and  then  heat  for  a  few  moments  until  the  mass  has  half 
fused,  stirring  constantly.     The  MnO2  has  been  converted  into  potassium 
manganate.     Treat  with  water,  decant  the  clear  green  liquid  and  place 
20  c.  c.  in  an  evaporating  dish  and  notice  any  changes  of  color.     Place 
another  portion  in  a  test  tube  and  add  a  few  drops  of  dilute  H2SC»4.     On 
account  of  these  changes  of  color,  potassium  manganate  is  called  chame- 
leon mineral. 

EXERCISE   42. — IRON. 

245.  Dissolve  2  or  3  small  tacks  in  8  or  10  c.  c.  of  dilute  sulphuric 
acid  in  a  small,  beaker ;  when  the  evolution  of  hydrogen  slackens,  dilute 
with  an  equal  bulk  of  water  and  filter  into  a  small  flask.     To  the  liquid 
add  a  few  drops  of  strong  nitric  acid,  and  heat  it  to  boiling.     The  liquor 
will  soon  be  colored  dark  brown  by  the  nitrous  fumes  resulting  from  the 
decomposition  of  the  nitric  acid,  which  are  for  a  short  time  held  dis- 
solved by  the  liquid ;  but  this   deep  coloration   soon   passes  away,  and 
there  is  left  only  the  yellowish  red  color  of  the  ferric  sulphate  which  has 
been  formed.     Add  to  the  solution  ammonia  water,  until  the  odor  of  the 
latter  persists  after  agitation,  and  collect  upon  a  filter  the  flocculent  red 
precipitate  of  ferric  hydrate. 

246.  Repeat  Expt.  217  but  make  use  of  the  Fe2H6O6  obtained  in 
Expt.  245.     Compare  the  solubility  of  Fe2O3  and  P'e2H6O6  in  HC1. 

247.  Compare  the  actions  of  the  dilute  acids  upon  metallic  iron. 


48 


248.  Pour  a  solution  of  copperas  into  an  open  capsule,  and  leave  it 
exposed  to  the  air  for  a  day  or  two  ;  the  solution  will  gradually  become 
yellow  as  the  oxidation  proceeds,  and  after  a  while  a  rusty  precipitate  of 
ferric  oxide,  or  of  highly  basic  ferric  sulphate,  will  fall. 

249.  Place  20  c.  c.  of  copperas  solution  in  an  evaporating  dish  and 
add  ammonia  water  in  excess.     Observe  the  color  of  the  precipitate. 
Allow  to  stand  for   half  an  hour,  stirring  frequently,  and  observe  any 
change  in  the  color  of  the  precipitate.     Write  the  equation. 

250.  Dip  a  small  piece  of  cotton  cloth  in  the  solution  of  nutgalls,  and 
allow  it  to  become  dry ;  then  dip  it  in  the  solution  of  copperas  and  hang 
it  up  in  damp  air.     Finally,  try  to  wash  out  the  color. 

251.  Dissolve  one  gram  of  copperas  (iron  sulphate)  in  100  c.  c.  of 
water  in  a  bottle  of  200  c.  c.  capacity.     Into  the  solution  stir  a  mixture 
of  i  gram  of  finely  powdered  indigo  and  1.5  grams  of  freshly  slaked  lime; 
fill  up  the  bottle  with  water  and  cork  it.     Shake  the  bottle  occasionally, 
and,  at  the  next  exercise,  pour  off,  or  remove  with  a  pipette,  a  portion  of 
the  clear  and  nearly  colorless  liquid  without  disturbing  the  precipitate 
In  the  bottom  of  the  bottle.     Expose  this  liquid  to  the  air  in  a  shallow 
dish. 

EXERCISE  43.  —  IRON,   COBALT,   AND  NICKEL. 

252.  Dissolve  a  small  crystal  of  copperas  in  water  and  add  to  the 
liquid  a  drop  or  two  of  a  solution  of  ammonium  sulphydrate. 

Finish  251. 

253.  To  a  solution  of  a  ferric  salt  add  a  few  drops  of  sulphocyanate 
of  potassium  and  notice  the  color.     This  is  a  very  delicate  test  for  iron. 

254.  Dissolve  2  or  3  iron  tacks  in  dilute  HC1.    Filter,  and  to  a  small 
portion  of  the  filtrate  add  a  few  drops  of  potassium  ferrocyanide  solu- 
tion.    To  a  similar  portion  of  the  filtrate  add  a  few  drops  of  potassium 
ferricyanide.     Notice  the  difference.     These  are  tests  for  ferrous  salts. 
Now  to  the  remaining  part  of  the  filtrate  add  a  few  drops  of  HNOs  and 
boil.     Test  small  portions  of  this  oxidized  filtrate  with  ferro-  and  ferri- 
cyanide of  potassium  and  show  the  results.     If  you  have  been  success- 
ful in  oxidizing  the  solution  divide    it  into  two  portions.     Through  the 
first  pass  H2S  and  note  the  effect.     To  the  second  add  SnCl2  and  warm, 
and  then  test  with  ferro-  and  ferri-  cyanide  of  potassium. 

255.  Prepare  a  borax  bead,  as  will  be  shown.     Place  upon  it  a  parti- 
cle of  any  cobalt  salt  and  heat  in  both  reducing  and  oxidizing  flame  be- 


49 

fore  the  blow-pipe.     Prepare  i  second  bead  and  add  a  nickel  salt.     The 
colors  obtained  are  good  tests  for  the  respective  metals. 

256.  Write  your  name  upon  a  piece  of  filter-paper,  using  CoCl2  solu- 
tion for  ink.     Allow  to  dry  and  observe   that   the  writing  is  invisible. 
Now  warm  gently  and  observe  the   effect.     Explain.     Finally  breathe 
upon  the  writing. 

257.  To  2  c.  c.  of  CoN2Oe  solution  add  an  equal  volume  of  dilute 
silicate  of  soda  solution. 

258.  Pour  5  c.  c.  of  a  solution  of  any  cobalt  salt  into  a  test  tube  and 
add  i  c,  c.  of  acetic  acid.     Now  add  an  equal  volume  of  potassium  nitrite 
solution.     Allow  to  stand  and  observe  the  precipitate.     It  is  a  double 
nitrite  of  potassium  and  cobalt,  and  its  formation  is  one  of  the  best  tests 
to  show  the  presence  of  cobalt. 

259.  Take  10  drops  or  less  of  a  solution  of  CoCl2.     Dilute  with 
water,  then  add  ammonia  water  to  alkaline  reaction ;  if  any  precipitate 
appears,  filter,  and  to  the  clear  filtrate  add  a  few  drops  of  NH4HS  solu- 
;tion  and  note  what   happens.     Now  take  the   same  amount  of  cobalt 
solution  as  before,  and  two  teaspoonfuls  of  NELtCl  solution,  then  add 
ammonia  to  alkaline  reaction,  note  what  happens  and  explain. 

260.  Heat  gently  in  a  dry  test  tube  a  few  crystals  of  NiCl2. 

261.  Take  two  test  tubes  and  place  in  one  2  c.  c.  of  Coda  and  in 
e  other  2  c.  c.  of  NiCl2.    Add  to  each  NaOH  to  alkaline  reaction,  then 

a  little  KCN  and  then  an  equal  volume  of  sodium  hypochlorite  and 
I  warm.  The  NiCl2  gives  a  dark  precipitate  of  NioIIeOe  while  the  CoCl2 
I  is  unaffected.  The  reaction  is  often  used  to  distinguish  nickel  in  the 

presence  of  cobalt. 

EXERCISE  44.  —  ARSENIC. 

[Use  great  caution  in  performing  all  the  experiments  in  this  exercise.] 

262.  Place  a  few  particles  of  "  arsenious  acid  "  in  an  open  tube  of 
lard  glass  about  10  c.  in.  long  and  heat  over  the  lamp,  holding  the  tube 
u  a  sloping  position.     Examine  the  sublimate  with  a  microscope. 

263.  Drop  into  the  point  of  a  drawn  out  tube  of  hard  glass,  No.  5,  a 
.norsel  of  arsfcnious  oxide,  and  above  it  place  a  splinter  of  charcoal ;   heat 
1  he  coal  red  hot  in  the  lamp  flame,  and  then  volatilize  the  arsenious  acid. 

264.  Throw  a  particle  of  arsenious  acid  upon  a  piece  of  red  hot  char- 
coal.   Notice  any  peculiar  odor. 


r 


50 

265.  [Under  the   Hood.]     Arrange  a  hydrogen  generator  as  in 
the   model,  having   a   delivery   tube   beyond  the  calcium  chloride  tube 
drawn   down   to   a  narrow  bore  in  several  places.     Generate  hydrogen 
from  zinc  and  dilute  chlorhydric  acid,  and  when  pure  hydrogen  escapes 
from  the  delivery  tube  light   the  jet.     Into  the   generator   through  the 
thistle  tube  pour  a  ^^=*  few  drops  «=4»$  of  a  solution  of  arsenious  acic 
in  chlorhydric  acid  ;  watch  the  flame  to  see  whether  it  appears  to  alter  in 
character.     Hold  a  concave  bit  of  cold  porcelain  in  the  flame ;  a  brownish 
black  deposit  of  arsenic  is  formed ;  collect  several  of  these  spots  and 
reserve  them  for  future  experiment.     While  the  stream  of  arseniuretec 
hydrogen  is  passing  through  the  delivery  tube,  heat  the  tube  with  the 
flame  of  a  Bunsen  lamp,  a  little  behind  one  of  the  constricted  portions 
The  arseniureted  hydrogen  is  decomposed,  and  arsenic  is  deposited  in 
the  tube  as  a  metallic  mirror.     Produce  several  of  these  mirrors  and  save 
them,  and  then  wash  out  the  generator,  zinc  and  all,  into  the  sink  under 
the  small  hood.     [This  is  Marsh's  test.] 

266.  Into  a  small  bottle  put  several  teaspoonfuls  of  a  chlorhydric 
acid  solution  of  arsenious  acid,  add  water  enough  to  nearly  fill  the  bottle 
and  allow   H2S  -to   bubble   through  the  liquid  until  the  liquid  smells 
strongly  of  sulphureted  hydrogen.     Collect  the  precipitate  (what  is  it?] 
upon  a  filter ;  and  test  its  solubility  in  HC1  and  Na2Sx  solution. 

267.  Take  two  test  tubes  and  place  in  each  5  c.  c.  of  arsenite  oi: 
sodium.     Make  one  strongly  acid  with  HC1  and  the  other  strongly  alka- 
line with  NaOH.     Pass  H2S  into  each  tube  and  note  the  result.    Explain. 
Acidulate  with  HC1  the  one  that  is  alkaline. 

268.  Take  two  test  tubes.     Place  in  one  5  c.  c.  of  arsenite  of  sodium, 
in  the  other  5  c.  c.  of  arseniate  of  sodium.     Acidify  with  HC1  and  pass  in 
H2S.     Explain. 

269.  Place  in  one  test  tube  5  c.  c.  of  arsenite  of  sodium,  and  in 
another  5  c.  c.  of  arseniate  of  sodium  and  add  a  few  drops  of  AgNOg  to 
each.    This  difference  is  the  distinguishing  test  between  the  two  acids 
and  their  salts.    Save  the  silver  residues. 

I 


EXERCISE  45. — ANTIMONY  AND   BISMUTH. 

270.  [Under  the  hood.]     In  a  flask  of  about  200  c.  c.  capacity,  heat 
gently  0.5  gram  of  finely  powdered   antimony  with   30  c.  c.  of  strong 
chlorhydric  acid,  to  which  ten  drops  of  nitric  acid  have  been   added. 
When  complete  solution  has  been  effected,  evaporate  to  less  than  one 
half  its  bulk ;  pour  a  little  of  the  chloride  into  water.     Evaporate  the  rest 
of  the  solution  to  the  consistency  of  a  thick  syrup ;  it  is  the  butter  of 
antimony. 

271.  Pour  some  of  the   antimony  terchloride  into  a  small  bottle 
nearly  full  of  water,  and  then  add  just  enough  chlorhydric  acid  to  dis- 
solve the  white  precipitate  which  is  formed.     Through  the  clear  solution 
pass  a  stream  of   hydrogen  sulphide.     Filter  and  test   the  solubility  of 
Sb2S3  in  dilute  HC1,  in  hot  strong  HC1,  and  in  Na2Sx. 

272.  Perform  precisely  as  265,  except  that  a  solution  of  an  antimony 
compound  is  to  be  substituted    for  the    solution   containing    arsenic. 
Reserve  the  mirrors  as  in  Expt.  265. 

273.  Compare  together  the  spots  obtained  on  porcelain  from  arse- 
niureted  hydrogen  (Expt.  265)  and  from  antimoniureted  hydrogen  (Expt. 
272).     i.  The  arsenical  spot  has  a  metallic  luster  and  a  brown   color 
when  thin  ;  the  stain  of  antimony  has  a  feeble  luster,  and  is  smoky  black. 
2.  The  arsenical  stain  disappears  readily  on  the  application  of  a  heat 
below  redness  ;  the  stain  of  antimony  is  volatile  only  at  a  red  heat.     On 
account  of  the  comparative  want  of  volatility  which  characterizes  the  anti- 
mony deposit,  the  mirrors  of  antimony  obtained  in  the   glass  tube  are 
always  deposited  nearer  the  heated  portion  of  the  tube  than  the  arsenic 
mirrors  are.     3.  The  arsenical   stains   may  be  distinguished,  moreover, 
from    the    antimonial   stains   by  means   of  "chloride   of    lime,"  which 
immediately  dissolves  arsenical  spots,  but  leaves  antimonial  spots  unaf- 
fected for  a  long  time.     4.  An  antimony  stain  will  dissolve  readily  in  a 
few  drops  of  a  solution  of  sulphydrate  of  ammonium  which  has  become 
yellow  by  keeping;    when  such  a  solution  is  evaporated  to  dryness,  a 
bright  orange  stain  remains.     The  arsenical  stain,  on  the  contrary,  is  not 
perceptibly  affected  by  the  yellow  sulphydrate  of  ammonium  solution, 
unless  heat  is  applied. 

274.  Connect  the  tube  of  hard  glass  in  which  the  arsenic  mirrors 
were  formed,  in  Expt.  265,  with  a  sulphureted  hydrogen  generator,  inter- 
posing between  the  tube  and  the  generator  a  suitable  drying-tube  or  bottle 
filled  with  calcium  chloride ;  then  transmit  through  the  tube  a  wry  slow 


52 

stream  of  hydrogen  sulphide  gas,  and  heat  the  mirrors  with  a  small  gas 
flame,  proceeding  from  the  outer  to  the  inner  border  of  the  mirrors  in 
the  direction  opposite  to  that  of  the  gas  current. 

Repeat  the  same  process  with  the  tube  containing  the  antimony  mirrors 
obtained  in  Expt.  272. 

275.  Place  5  c.  c.  of  tartar  emetic  (tartrate  of  antimony  and  potas- 
sium) in  each  of  two  test  tubes,  and  make  one  slightly  acid  with  HC1  and 
and  the  other  strongly  alkaline  with   NaOH,  and  saturate  with  H^S. 
Explain. 

276.  Repeat  Expt.  270  but  use  bismuth. 

277.  Repeat  Expt.  275  but  use  Bids  instead  of  tartar  emetic. 

278.  Weigh  out  15  grams  of  bismuth,  8  grains  of  lead  and  8  grams 
of  tin.     Heat  a  beaker  of  water  to  boiling,  and  convince  yourself  that 
neither  the  bismuth,  lead  or  tin  will  melt  in  the  hot  water.     Now  fuse  the 
metals  together  in  an  iron  spoon.     Allow  the  mass  to  cool  and  place  it 
in   a  beaker  of  boiling  water.     This   alloy  is  known  as  fusible   metal. 
Pour  a  little  of  the  fused  metal  into  a  narrow  test  tube  and  allow  to  cool. 
Explain  its  action. 


EXERCISE  46. — CHEMICAL  CHANGES. 


Analyze  the  following  reactions,  and  tell  whether  they  are  analytical, 
synthetical,  or  metathetical.  Also  explain  any  modifications  from  the 
action  which  would  be  naturally  expected. 

1.  To  0.5  c.  c.  of  sodic  carbonate  solution  add  dilute  HC1. 

2.  Place  a  bit  of  copper  in  a  test  tube  and  add  dilute  HNOs. 

3.  Repeat  Expt.  88.     Test,  before  warming,  for  SO2,  and  again  after 
warming. 

4.  Mix  2  grams  NFLiCl  and  2  grams  CaH2O2-     Place  in  a  dry  test 
tube  and  test  for  NH3.     Now  warm  and  repeat  the  test. 

5.  To  5  c.  c.  of  sodium  hyposulphite  solution  add  dilute  HC1.     To  a 
second  5  c.  c.  add  acetic  acid. 

6.  Place  5  c.  c.  of  CuSO4  solution  in  each  of  three  test  tubes.     To 
one  add  an  equal  volume  of   NaCl  solution,  to  another  a  few  c.  c.  of 
BaCl2  solution  and  compare  the  three  tubes. 

7.  Shake    a    few    grams     of     CaSO*   with    water,  filter    and    add 
(NH4)2C03. 


53 

8.  Take  2  c.  c.  of  a  solution  of  As2O3  in  HC1  and  dilute  to  10  c.  c. 
with  water.     Add  (NH.i)oSx  drop  by  drop  at  first,  finally  a  large  excess 
.UK!  boil.     Now  acidify  with  HCL 

9.  Repeat  the  last  experiment,  but  use  CdCl2  instead  of  As2O3. 

10.  Place  3  c.  c.  of  Fe2Cle  in  each  of  two  test  tubes  and  dilute  with 
20  c.  c.  of  water.     To  one  add  a  few  drops  of  K4FeCye,  to  the  other 
a  few  drops  of  KSCN. 

11.  Into  a  test  tube  put  10  c.  c.  of  water.     Add  to  it  3  drops  of 
KSCN  solution;  then  add  one  drop  of  Fe2  (NO3)6.     Now  add  AgNO3 
solution  drop  by  drop  until  there  is  a  change  of  color.     Explain.     Save 
all  silver  residues. 

12.  To  5  c.  c.  of  CuSO4  solution  add  NH4OH  in  excess. 

13.  Heat  a  mixture  of  mercuric  sulphate  and  sodic  chloride  in  a 
matrass. 

14.  Pass   a  current  of   CO2  through  a  dilute   solution  of  sodium 
silicate. 


EXERCISES   47    AND   48.  —  PRINCIPLES   OF   QUALITATIVE  ANALYSIS. 

1.  Take  i  c.  c.  of  an  aqueous  solution  of  CuSO4  and  i  c.  c  of  AgNOs 
solution.     Add  dilute  HC1  a  few  drops  at  a  time ;  shake  and  allow  to 
settle  after  each  addition.     When  further  addition  of  HC1  produces  no 
further  precipitation  (of  what?     Answer  from  past  experience),  collect 
the  precipitate  on  a  filter.     To  the  filtrate  add  ammonia  little  by  little 
to  alkaline  reaction  and  explain   the    observed  result    (also  from   past 
experience). 

2.  Take  about  i  c.  c.  of  each  of  the  following  solutions  and  add  to 
each,  in  a  test  tube,  a  few  drops  of  HC1  (dilute):—  AgNO3,  PbN2OG, 
CuN2O6,  Hg2N2O6,  HgN2O6,  FeSO4,  ZnSO4,  MgSO4,  KNO3.      Note  in 
which  cases  a  precipitate  appears. 

3.  To  i  c.  c.  of  a  solution  of  AgNO3  add  z  c.  c.  or  so  of  water  and 
then  HC1  (dilute)  a  little  at  a  time  with  shaking  unti)  further  addition 
produces  no  more  precipitate.     Wash  by  decantation.     Boil  one  portion 
of  precipitate  with  water;  treat  a  second  portion  with  ammonia  water. 

Repeat  this  procedure,  using  a  solution  of  PbN2Oe  instead  of  AgNO3, 
also  using  Hg2N2Oe.  To  small  portions  of  solutions  of  AgNOg,  PbN2O$ 
and  Hg2N2O6,  add  H2SO4  (dilute). 


54 

4.     Mix   together   some    of    each   of    the    three    solutions   (AgNOg, 
PbN2Oe,  Hga^Oe),  and  proceed  as  indicated  in  the  following  scheme. 
Add  HC1  and  filter. 


I  I 

Filtrate.  Precipitate  (wash). 

Throw  away.      Transfer  to  a  test  tube,  add  water  and 
boil  several  times;  filter  or  decant. 

| 

I  I 

Filtrate.  Precipitate. 

Add  dil.  H2SO4.  Add  NH4OH  and  warm  ;  filter. 


I  I 

Filtrate.  Precipitate. 

Add  dil.  HNO3  Dry,  mix  with  Na2CO3, 

to  acid  reaction.  and  heat  in  a  matrass. 

Then  take  an  unknown  solution  which  may  contain  compounds  of  one  or 
more  of  the  elements  lead,  silver  or  mercury  (ous). 

5.  Three  general  methods  by  which  the  presence  of  a  given  element 
may  be  ascertained. 

1.  By  isolating  the  element  itself.     Recall  or  perform,  if  you  do  not 
remember  exactly  what  happened,  Expts.  215,  234,  188. 

2.  By  producing  a  characteristic  compound  of  the  element  sought,  as 
we  have  already  proved  the  presence  of  Ag,  Pb  or  [Hg2]  "  by  the  appear- 
ance and  action  of  their  chlorides." 

3.  By  producing  a  precipitate  not  containing  the  element  sought,  but 
which  could  be  formed  only  in  presence  of  that  element  or  some  partic- 
ular compound  of  it.     Expt.  227.     The  precipitate  is  mercurous  chloride 
(Hg2Cl2)  and  the  HgCl2  may  be  used  as  a  test  for  tin. 

2  HgCl2  +  SnCl2  =  SnCl4  +  Hg2Cl2. 

6.  Make  a  solution  containing  say  i  c.  c.  of  each  of  the  following 
solutions:  Fe2Cl6,  ZnCl3,  CaCl2,  MgCl2,  and  a  teaspoonful  of  NH4C1. 
Add  ammonia  until  the  odor  persists  after  shaking,  collect  the  precipi- 
tated Fe8HjjO6  on  a  filter,  and  to  the  filtrate  add  (NH4)HS.     Collect  the 


55 

precipitated  ZnS  on  a  filter  and  to  the  filtrate  add  (NH^COs.  Collect 
the  precipitated  CaCO3  on  a  filter  and  to  the  filtrate  add  Na2HPO4. 
The  precipitate  is  a  phosphate  of  Mg  and 


EXERCISES   49-53.  —  PREPARATIONS.    ' 

1.  Purification  of  Sal- Ammoniac. 

Place  100  grams  of  commercial  NH4C1  in  a  six- inch  evaporating  dish 
:md  add  300  c.  c.  of  water.  Heat  and  stir  until  the  NH^Cl  has  dissolved. 
Add  a  few  c.  c.  of  NH^OH  to  precipitate  any  iron  present,  and  filter  while 
hot  through  a  large  filter.  The  filtrate  should  be  colorless.  Carefully 
wash  the  dish  and  return  the  filtrate  to  it  and  evaporate  with  continual 
stirring.  Continue  the  evaporation  not  too  rapidly  until  the  NH^Cl  is 
obtained  as  a  fine  white  powder  free  from  lumps.  Weigh. 

2.  Glauber's  Salt. 

Place  200  c.  c.  of  water  in  a  beaker  which  will  hold  500  c.  c.  Weigh  in 
a  small  beaker  20  grams  of  H^SO^  and  pour  this  slowly  into  the  200  c.  c. 
of  water.  Weigh  60  grams  of  sal -soda  and  dissolve  by  warming  in  the 
least  possible  quantity  of  water.  Add  the  solution  of  sal- soda  little  by 
little  to  the  dilute  H2SO4,  carefully  avoiding  all  loss  by  foaming.  Test 
with,  litmus  paper,  and  if  the  liquid  is  still  acid,  add  sal- soda  solution 
until  it  has  become  slightly  alkaline.  Evaporate  in  a  large  dish  to  one 
third  of  the  original  volume  and  filter  while  hot.  Set  the  filtrate  aside 
in  the  dish  until  the  next  exercise.  Cover  the  dish  with  paper  to  protect 
it  from  dust.  Pour  off  the  supernatant  liquid  from  the  crystals  when 
they  are  formed. 

3.  Ammonium  Iron  Alum.  \ 
Ferric  Sulphate.  —  Weigh  30  grams  of  H^SO^  in  a  beaker  and  dilute 

with  15  c.  c.  of  water.  Stir  thoroughly  into  the  acid  20  grams  of 
Fe2H6Oc.  Add  20  c.  c.  of  water,  warm  gently  and  stir  frequently  while 
the  ammonium  sulphate  (see  below)  is  being  prepared.  The  Fe2H0O6 
will  gradually  dissolve.  Finally  dilute  with  water,  filter  and  evaporate 
until  the  liquid  becomes  turbid  from  the  separation  of  the  ferric  sul- 
phate. Mix  this  solution  with  that  of  the  ammonium  sulphate  prepared 
in  the  mean  time,  stir,  cover  with  paper  and  set  aside  until  the  next 
exercise. 


56 

Ammonium  Sulphate.  —  Weigh  10  grams  of  H2SO4  and  place  it  in  an 
evaporating  dish.  Dilute  with  25  c.  c.  of  water.  Now  add  in  small  por- 
tions ammonia  until  a  permanent  smell  of  the  same  is  obtained  after 
stirring  the  liquid.  Filter  and  evaporate  to  1 5  c.  c. 

4.  Sugar  of  Lead. 

Place  20  grams  of  PbO  in  an  evaporating  dish,  cover  with  water  and 
reduce  to  a  thin  paste  with  a  pestle.  Add  45  grams  of  HO(C2H3O) 
and  warm  until  the  PbO  has  dissolved.  Filter  and  evaporate  until  a 
drop  of  the  liquid  cooled  upon  a  watch  glass  deposits  numerous  crystals. 
Cover  and  allow  to  stand. 

5.  Barium  Carbonate. 

Dissolve  1 8  grams  of  BaCl2  in  150  c.  c.  of  water  by  warming  in  a  flask, 
filter  and  pour  into  a  large  bottle.  Powder  in  a  porcelain  mortar  some 
(NH^COs  and  weigh  out  6  grams.  To  this  add  10  c.  c.  of  ammonia 
water  and  then  10  c.  c.  of  water,  and  stir  without  warming  until  the 
(NH4)2CO3  is  dissolved.  Filter  if  necessary.  Pour  the  solution  of 
(NH4)2CO3  into  the  solution  of  BaCl2,  shake  well  and  allow  to  settle. 
Pour  a  few  c.  c.  of  the  liquid  on  the  top  into  a  test  tube  and  add  a  little 
(NH^COg.  If  a  precipitate  is  obtained,  more  (NH4)2CO3  must  be 
added  to  the  BaCl2.  Repeat  the  test  until  a  small  excess  of  (NH^COa 
is  present.  Allow  the  precipitate  to  settle  and  wash  by  decantation  four 
times.  Test  the  last  wash-water  with  AgNO3  for  chlorine.  If  chlorine 
is  present  in  any  considerable  quantity,  continue  to  wash  by  decantation 
until  only  a  trace  remains.  Then  filter,  wash  and  dry  the  precipitate 
carefully,  and  give  the  BaCO3  to  the  assistant. 

6.  Chrome  Yellow. 

Dissolve  25  grams  of  sugar  of  lead  in  50  c.  c.  of  water  and  filter.  Pour 
the  solution  into  a  large  bottle.  Dissolve  10  grams  of  bichromate  of 
potassium  in  20  c.  c.  of  water  and  pour  this  solution  into  the  one  of  sugar 
of  lead  in  the  large  bottle  and  shake.  Add  100  c.  c.  of  water  and  allow 
the  precipitate  to  subside,  and  if  the  supernatant  liquid  is  yellow  add  a 
further  small  quantity  of  sugar  of  lead  solution  and  shake  again.  Con- 
tinue this  until  the  sugar  of  lead  is  present  in  slight  excess.  Fill  the 
bottle  full  of  water  and  wash  the  precipitate  by  decantation  until  the 
wash-water  gives  no  further  brown  color  when  H2S  is  passed  through  it. 
Now  bring  the  precipitate  upon  a  filter. 


57 


7«     Chrome  Orange. 

Take  one  half  of  the  precipitate  obtained  in  the  last  experiment,  place 
it  in  a  small  evaporating  dish,  add  a  few  c.  c.  of  water  and  rub  carefully 
with  a  pestle  until  all  the  lumps  are  broken  up.  Dissolve  3  grams  of 
NaOH  in  10  c.  c.  of  water  and  pour  this  solution  upon  the  chrome  yel- 
low, stir  constantly  and  keep  at  the  boiling  point  for  10  minutes.  Pour 
into  the  bottle,  taking  care  to  wash  out  all  adhering  chrome  orange. 
Wash  now  by  decantation  until  the  wash-water  gives  no  further  test  for 
an  alkali  with  litmus  paper.  Filter,  dry  and  weigh.  Give  both  chrome 
yellow  and  chrome  orange  to  assistant. 


APPENDIX. 


CHEMICAL   MANIPULATION. 

1.  Glass-tubing.  —  Two  qualities  of  glass-tubing  are  used  in  chem- 
ical experiments,  —  that  which  softens  readily  in  the  flame  of  a  gas-  or 
spirit-lamp,  and  that  which  fuses  with  extreme  difficulty  in  the  flame 
of  the  blast-lamp.  These  two  qualities  are  distinguished  by  the 
terms  soft  and  hard  glass.  Soft  glass  may  be  used  for  all  purposes, 
except  the  intense  heating,  or  ignition,  of  dry  substances.  Fig.  I 
represents  the  most  convenient  sizes  of  glass-tubing,  both  hard  and 
soft,  and  shows  also  the  proper  thickness  of  the  glass  walls  for  each 
size. 

FIG.  i. 


8      7 


2.  Cutting  and  Cracking  Glass.  —  Glass-tubing  and  glass-rod 
must  generally  be  cut  to  the  length  required  for  any  particular  ap- 
paratus. A  sharp  triangular  file  is  used  for  this  purpose.  The  stick 
of  tubing,  or  rod,  to  be  cut  is  laid  upon  a  table,  and  a  deep  scratch  is 
made  with  the  file  at  the  place  where  the  fracture  is  to  be  made.  The 
stick  is  then  grasped  with  the  two  hands,  one  on  each  side  of  the 
25 


II  APPENDIX. 

mark,  while  the  thumbs  are  brought  together  just  at  the  scratch.  By 
pushing  with  the  thumbs  and  pulling  in  the  opposite  direction  with 
the  fingers,  the  stick  is  broken  squarely  at  the  scratch,  just  as  a  stick 
of  candy  or  a  dry  twig  may  be  broken.  The  sharp  edges  of  the  fracture 
should  invariably  be  made  smooth,  either  with  a  wet  file,  or  by  soften- 
ing the  end  of  the  tube  or  rod  in  the  lamp.  (See  Appendix,  §  3.) 
Tubes  or  rods  of  sizes  4  to  8  inclusive  may  readily  be  cut  in  this  man- 
ner ;  the  larger  sizes  are  divided  with  more  difiiculty,  and  it  is  often 
necessary  to  make  the  file-mark  both  long  and  deep.  An  even  frac- 
ture is  not  always  to  be  obtained  with  large  tubes.  The  lower  ends 
of  glass  funnels,  and  those  ends  of  gas  delivery- tubes  which  enter  the 
bottle  or  flask  in  which  the  gas  is  generated,  should  be  filed  off,  or 
FIG.  II.  ground  off  on  a  grindstone,  obliquely  (Fig.  II),  to 

facilitate  the  dropping  of  liquids  from  such  extremi- 
ties. 

In  order  to  cut  glass  plates,  the  glazier's  diamond 
must  be  resorted  to.  For  cutting  exceedingly  thin 
glass  tubes  and  other  glass  ware,  like  flasks,  retorts 
and  bottles,  still  other  means  are  resorted  to,  based  upon  the  sudden 
and  unequal  application  of  heat.  The  process  divides  itself  into 
two  parts,  the  producing  of  a  crack  in  the  required  place,  and  the 
subsequent  guiding  of  this  crack  in  the  desired  direction.  To  pro- 
duce a  crack,  a  scratch  must  be  made  with  the  file,  and  to  this  scratch 
a  pointed  bit  of  red-hot  charcoal,  or  the  jet  of  flame  produced  by 
the  mouth  blowpipe,  or  a  very  fine  gas-flame,  or  a  red-hot  glass-rod 
may  be  applied.  If  the  heat  does  not  produce  a  crack,  a  wet  stick  or 
file  may  be  touched  upon  the  hot  spot.  Upon  any  part  of  a  glass  sur- 
face except  the  edge,  it  is  not  possible  to  control  perfectly  the  direc- 
tion and  extent  of  this  first  crack  ;  at  an  edge  a  small  crack  may  be 
started  with  tolerable  certainty  by  carrying  the  file-mark  entirely  over 
the  edge.  To  guide  the  crack  thus  started,  a  pointed  bit  of  charcoal 
or  slow-match  may  be  used.  The  hot  point  must  be  kept  on  the  glass 
from  1  c.  m.  to  0.5  c.  m.  in  advance  of  the  point  of  the  crack.  The 
crack  will  follow  the  hot  point,  and  may  therefore  be  carried  in  any 
desired  direction.  By  turning  and  blowing  upon  the  coal  or  slow- 
match,  the  point  may  be  kept  sufficiently  hot.  Whenever  the  place 
of  experiment  is  supplied  with  common  illuminating  gas,  a  very  small 
jet  of  burning  gas  may  be  advantageously  substituted  for  the  hot  coal 
or  slow  match.  To  obtain  such  a  sharp  jet,  a  piece  of  hard  glass 
tube,  No.  5,  10  c.  m.  long,  and  drawn  to  a  very  fine  point  (see  Ap- 


APPENDIX. 


pendix  §  3),  should  be  placed  in  the  caoutchouc  tube  which  ordinarily 
delivers  the  gas  to  the  gas-lamp,  and  the  gas  should  be  lighted  at  the 
fine  extremity.  The  burning  jet  should  have  a  fine  point,  and  should 
not  exceed  1.5  c.  in.  in  length.  By  a  judicious  use  of  these  simple 
tools,  broken  tubes,  beakers,  flasks,  retorts  and  bottles  may  often  be 
made  to  yield  very  useful  articles  of  apparatus.  No  sharp  edges 
should  be  allowed  to  remain  upon  glass  apparatus.  The  durability 
of  the  apparatus  itself,  and  of  the  corks  and  caoutchouc  stoppers  and 
tubing  used  with  it,  will  be  much  greater,  if  all  sharp  edges  are  re- 
moved with  the  file,  or,  still  better,  rounded  in  the  lamp. 

3.  Bending  and  Closing  Glass-tubes.  —  Tubing  of  sizes  5 
to  8  inclusive  can  generally  be  worked  in  the  common  gas-  or  spirit- 
lamp  ;  for  larger  tubes  the  blast-lamp  is  necessary  (see  Appendix, 
§  6).  Glass  tubing  must  not  be  introduced  suddenly  into  the  hottest 
part  of  the  flame,  lest  it  crack.  Neither  should  a  hot  tube  be  taken 
from  the  flame  and  laid  at  once  upon  a  cold  surface.  Gradual  heating 
and  gradual  cooling  are  alike  necessary,  and  are  the  more  essential 
the  thicker  the  glass ;  very  thin  glass  will  sometimes  bear  the  most 
sudden  changes  of  temperature,  but  thick  glass  and  glass  of  uneven 
thickness  absolutely  require  slow  heating  and  annealing.  When  the 
end  of  a  tube  is  to  be  heated,  as  in  rounding  sharp  edges,  more  care  is 
required  in  consequence  of  the  great  facility  with  which  cracks  start 
at  an  edge.  A  tube  should,  therefore,  always  be  brought  first  into  the 
current  of  hot  air  beyond  the  actual  flame  of  the  gas-  or  spirit-lamp, 
and  there  thoroughly  warmed,  before  it  is  introduced  into  the  flame 
itself.  If  a  blast-lamp  is  employed,  the  tube  may  be  warmed  in  the 
smoky  flame,  before  the  blast  is  turned  on,  and  may  subsequently  be 
annealed  in  the  same  manner  ;  the  deposited  soot  will  be  burnt  off  in 
the  first  instance,  and  in  the  last,  may  be  wiped  off  when  the  tube  is 
cold.  In  heating  a  tube,  whether  for  bending,  drawing  or  closing, 
the  tube  must  be  constantly  turned  between  the  fingers,  and  also 
moved  a  little  to  the  right  and  left,  in  order  that  it  may  be  uniformly 
heated  all  around,  and  that  the  temperature  of  the  neighboring  parts 
may  be  duly  raised.  If  a  tube,  or  rod,  is  to  be  heated  at  any  part  but 
an  end,  it  should  be  held  between  the  thumb  and  first  two  fingers  of 
each  hand  in  such  a  manner  that  the  hands  shall  be  below  the  tube,  or 
rod,  with  the  palms  upward,  while  the  lamp-flame  is  between  the 
hands.  When  the  end  of  a  tube,  or  rod,  is  to  be  heated  it  is  best  to 
begin  by  warming  the  tube,  or  rod,  about  2  c.  m.  from  the  end,  and 
from  thence  to  proceed  slowly  to  the  end, 


tv  APPENDIX. 

The  best  glass  will  not  be  blackened  or  discolored  during  heating. 
The  blackening  occurs  in  glass  which,  like  ordinary  flint  glass,  contains 
lead  (silicate).  Glass  containing  much  lead  is  not  well  adapted  for 
chemical  uses.  The  blackening  may  sometimes  be  removed  by  put- 
ting the  glass  in  the  upper  or  outer  part  of  the  flame,  where  the 
reducing  gases  are  consumed,  and  the  air  has  the  best  access  to  the 
glass.  The  blackening  may  be  altogether  avoided  by  always  keeping 
the  glass  in  the  oxidizing  part  of  the  flame. 

Glass  begins  to  soften  and  bend  below  a  visible  red  heat.  The  con- 
dition of  the  glass  is  judged  of  as  much  by  the  fingers  as  the  eye  ;  the 
hands  feel  the  yielding  of  the  glass,  either  to  bending,  pushing  or 
pulling,  better  than  the  eye  can  see  the  change  of  color  or  form.  It 
may  be  bent  as  soon  as  it  yields  in  the  hands,  but  can  be  drawn  out 
only  when  much  hotter  than  this.  Glass-tubing,  however,  should  not 
be  bent  at  too  low  a  temperature  ;  the  curves  made  at  too  low  a  heat 
are  apt  to  be  flattened,  of  unequal  thickness  on  the  convex  and  con- 
cave sides,  and  brittle, 

In  bending  tubing  to  make  gas  delivery-tubes  and  the  like,  attention 
should  be  paid  to  the  following  points  :  1st,  the  glass  should  be  equally 
hot  on  all  sides  ;  2d,  it  should  not  be  twisted,  pulled  out  or  pushed 
together  during  the  heating  ;  3d,  the  bore  of  the  tube  at  the  bend 
should  be  kept  round,  and  not  altered  in  size  ;  4th,  if  two  or  more 
bends  be  made  in  the  same  piece  of  tubing  (Fig.  Ill,  a),  they  should 
all  be  in  the  same  plane,  so  that  the  finished  tube  will  lie  flat  upon 
the  level  table. 

When  a  tube  or  rod  is  to  be  bent  or  drawn  close  to  its-  extremity,  a 
temporary  handle  may  be  attached  to  it  by  softening  the  end  of  the 
tube,  or  rod,  and  pressing  against  the  soft  glass  a  fragment  of  glass 
tube,  which  will  adhere  strongly  to  the  softened  end.  The  handle 
may  subsequently  be  removed  by  a  slight  blow,  or  by  the  aid  of  a  file. 
If  a  considerable  bend  is  to  be  made,  so  that  the  angle  between  the 
arms  will  be  very  small  or  nothing,  as  in  a  siphon,  for  example,  the 
curvature  can  not  be  well  produced  at  one  place  in  the  tube,but  should 
FIG.  m.  be  made  by  heating,  progressively,  several  cen- 

timetres of  the  tube,  and  bending  continuous- 
ly from  one  end  of  the  heated  portion  to  the 
other  (Fig.  Ill,  &).  Small  and  thick  tube  may 
be  bent  more  sharply  than  large  or  thin  tube. 

In  order  to  draw  a  glass  tube  down  to  a  finer  bore,  it  is  simply 
necessary  to  thoroughly  soften  on  all  sides  one  or  two  centimetres' 


a 


APPENDIX.  v 

length  of  the  tube,  and  then,  taking  the  glass  from  the  flame,  to 
pull  the  parts  asunder  by  a  cautious  movement  of  the  hands.  The 
larger  the  heated  portion  of  glass,  the  longer  will  be  the  tube 
thus  formed.  Its  length  and  fineness  also  increase  with  the  rapidity 
of  motion  of  the  hands.  If  it  is  desirable  that  the  finer  tube 
should  have  thicker  walls  in  proportion  to  its  bore  than  the  origi- 
nal tube,  it  is  only  necessary  to  keep  the  heated  portion  soft  for  two 
or  three  minutes  before  drawing  out  the  tube,  pressing  the  parts 
slightly  together  the  while.  By  this  process  the  glass  will  be  thick- 
ened at  the  hot  ring. 

To  obtain  a  tube  closed  at  one  end,  it  is  best  to  take  a  piece  of 
tubing,  open  at  both  ends,  and  long  enough  to  make  two  closed  tubes. 
In  the  middle  of  the  tube  a  ring  of  glass,  as  narrow  as  possible,  must  be 
made  thoroughly  soft.  The  hands  are  then  separated  a  little,  to  cause 
a  contraction  in  diameter  at  the  hot  and  soft  part.  The  point  of  the 
flame  must  now  be  directed,  not  upon  the  narrowest  part  of  the  tube, 
but  upon  what  is  to  be  the  bottom  of  the  closed  tube.  This  point 
is  indicated  by  the  line  a  in  Fig.  IV.  By  FIG.  rv. 

withdrawing  the  right  hand,  the  narrow  part  ^ 

of  the  tube  is  attenuated,  and  finally  melted 
off,  leaving  both  halves  of  the  original  tube 
closed  at  one  end,  but  not  of  the  same  form  ; 
the  right-hand  half  is  drawn  out  into  a  long 

point,  the  other  is  more  roundly  closed.  It  is  not  possible  to  close 
handsomely  the  two  pieces  at  once.  The  tube  is  seldom  perfectly 
finished  by  the  operation  ;  a  superfluous  knob  of  glass  generally 
remains  upon  the  end.  If  small,  it  may  be  got  rid  of  by  heating  the 
whole  end  of  the  tube,  and  blowing  moderately  with  the  mouth  into 
the  open  end.  The  knob  being  hotter,  and  therefore  softer  than  any 
other  part,  yields  to  the  pressure  from  within,  spreads  out  and  disap- 
pears. If  the  knob  is  large,  it  may  be  drawn  off  by  sticking  to  it  a 
fragment  of  tube,  and  then  softening  the  glass  above  the  junction. 
The  same  process  may  be  applied  to  the  too  pointed  end  of  the  right- 
hand  half  of  the  original  tube,  or  to  any  misshapen  result  of  an  unsuc- 
cessful attempt  to  close  a  tube,  or  to  any  bit  of  tube  which  is  too  short 
to  make  two  closed  tubes.  When  the  closed  end  of  a  tube  is  too  thin, 
it  may  be  strengthened  by  keeping  the  whole  end  at  a  red  heat  for  two 
or  three  minutes,  turning  the  tube  constantly  between  the  fingers.  It 
may  be  said  in  general  of  all  the  preceding  operations  before  the 
lamp,  that  success  depends  on  keeping  the  tube  to  oe  heated  in  constant 


vi  APPENDIX. 

rotation,  in  order  to  secure  a  uniform  temperature  on  all  sides  of  the 
tube. 

9.  (Abridged.)  Corks.  —  The  best  corks  generally  need  to  be  soft- 
ened before  using;  this  may  be  effected  by  rolling  the  cork  under  a 
board  upon  a  table,  or  under  the  foot  upon  a  clean  floor,  or  by  gently 
squeezing  it  on  all  sides  with  a  "  cork-squeezer." 

In  boring  holes  through  corks  to  receive  glass  tubes  use  is  made  of  a 
round  file,  and  the  aim  is  to  make  the  hole  as  cylindrical  as  possible 
and  not  too  large. 

A  flask  which  presents  sharp  or  rough  edges  at  the  mouth  can 
seldom  be  tightly  corked,  for  the  cork  cannot  be  introduced  into  the 
neck  without  being  cut  or  roughened ;  such  sharp  edges  must  be 
rounded  in  the  lamp.  In  thrusting  glass  tubes  through  bored  corks : 
(1.)  The  tube  should  be  grasped  very  close  to  the  cork,  in  order  to 
escape  cutting  the  hand  which  holds  the  cork,  should  the  tube  break. 
(2.)  A  thistle  tube  must  never  be  held  by  the  thistle  in  driving  it 
through  the  cork,  nor  a  bent  tube  grasped  at  the  bend,  unless  the  bend 
comes  immediately  above  the  cork.  (3.)  The  tube  must  not  be  pushed 
straight  into  the  cork,  but  screwed  in,  as  it  were,  with  a  slow  rotary  as 
well  as  onward  motion.  Joints  made  with  corks  should  always  be 
tested  before  the  apparatus  is  used  by  blowing  into  the  apparatus  and 
at  the  same  time  stopping  up  all  legitimate  outlets.  Any  leakage  is 
revealed  by  the  disappearance  of  the  pressure  created. 

15.  Filtering. — Filtration  is  resorted  to  in  order  to  separate  a 
finely  divided  solid  from  a  liquid.  The  filter  may  be  made  of  paper, 
cloth,  tow,  cotton,  asbestos,  and  other  substances.  Paper  is  the  sub- 
stance oftenest  used.  A  good  filtering  paper  must  be  porous  enough 
to  filter  rapidly,  and  yet  sufficiently  close  in  texture  to  retain  the 
finest  powders  ;  and  it  must  also  be  strong  enough  to  bear,  when  wet, 
the  pressure  of  the  liquid  which  must  be  poured  upon  it. 

Filtering  paper  is  commonly  sold  in  sheets,  which  may  be  cut  into 
circles  of  any  desired  diameters  for  use,  according  to  the  various 
scales  of  operation  and  quantities  of  liquids  to  be  filtered,  or  pack- 
ages of  "  cut-filters  "  may  be  procured  ready-made  from  the  dealers 
in  chemical  ware. 

There  are  two  ready  methods  of  preparing  filters  for  use.  Accord- 
ing to  the  first  method,  shown  in  Fig.  XXIV,  a  circle  of  paper  is 
folded  over  on  its  own  diameter,  and  the  semicircle  thus  obtained 
is  doubled  once  upon  itself  into  the  form  of  a  quadrant ;  the  paper  thus 
folded  is  opened  so  that  three  thicknesses  shall  come  upon  one 'side, 


XXIV 


APPENDIX. 


Fie.  xxiv.  and  one  thickness  upon  the  other,  as  shown  in  the 
upper  half  of  Fig.  XXIV  ;  the  filter  is  then  placed 
in  a  glass  funnel,  the  angle  of  which  should  be  pre- 
cisely that  of  the  opened  paper,  viz.,  60°.  The 
paper  may  be  so  folded  as  to  fit  a  funnel  whose 
angle  is  more  or  less  than  60°,  but  this  is  the 
most  advantageous  angle,  and  funnels  should  be 
selected  with  reference  to  their  correctness  in  this 
respect. 

In  the  second  method  of  folding  filters,  the  circle  of  paper  is 
doubled  once  upon  itself  as  before  into  the  form  of  a  semicircle,  and 
a  fold  equal  to  one  quarter  of  this  semicircle  is  turned  down  on  each 
side  of  the  paper.  Each  of  the  quarter  semicircles  is  then  folded 
back  upon  itself,  as  shown  in  the  lower  half  of  Fig. 
XXV  ;  the  filter  is  opened,  without  disturbing  the 
folded  portions,  and  placed  in  the  funnel.  Filtration 
can  be  rapidly  effected  with  this  kind  of  filter,  for 
the  projecting  folds  keep  open  passages  between  the 
filter  and  the  funnel,  and  thus  facilitate  the  passage 
of  the  liquid.  That  portion  of  the  circle  of  paper 
which  must  necessarily  be  folded  up  in  order  to  give 
the  requisite  conical  form  to  a  paper  filter  retards 
filtration  in  the  first  manner  of  folding,  but  helps  it  in  the  second. 


FIG.  XXV. 


Fia.  XXVI. 


FIG.  xxvn. 


Coarse  and  rapid  fil- 
tering can  be  effected 
with  cloth  bags ;  also 
"by  plugging  the  neck 
of  a  funnel  loosely 
with  tow  or  cotton.  If 
a  very  acid  or  very 
caustic  liquid,  which 
•would  destroy  paper, 
cotton,  tow  or  wool, 
is  to  be  filtered,  th 
best  substances  wherewith  to 
the  neck  of 


plug 
the  funnel  are  asbestos 


and  gun-cotton,  neither  of  which  is 
attacked  by  such  corrosive  liquids. 
The  glass  funnel  which  holds  the  filter  generally  requires  an  inde- 
pendent support,  for  it  is  seldom  judicious,  or  possible,  to  support 


APPENDIX.  xxv 

the  funnel  directly  upon  the  vessel  which  receives  the  filtrate,  as  tho 
clear  liquid  which  rues  through  the  filter  is  called.  The  iron  stand 
(Fig.  XVII)  may  be  used  for  this  purpose ;  and  wooden  stands,  of  the 
form  represented  in  Fig.  XXVI,  adapted  expressly  for  holding  funnels, 
are  very  convenient  and  not  expensive.  In  general,  care  should  bo 
taken  that  the  lower  end  of  the  funnel  touch  the  side  or  edge  of  the 
vessel  into  which  the  filtrate  descends,  in  order  that  the  liquid  may  not 
fall  in  drops,  but  run  quietly  down  without  splashing.  Sometimes 
there  is  no  objection  to  thrusting  a  funnel  directly  into  the  neck  of  a 
bottle  or  flask,  but  in  this  case  an  ample  exit  for  the  air  in  the  bottle 
must  be  provided  (Fig.  XXVII). 

[The  "  Appendix  "  is  taken  from  Eliot  and  Storer's  Elementary  Man- 
ual by  permission  of  the  authors  and  publishers.] 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 


29May'6JDH 

~77. — 777-7 


5  1961 


LD  21A-50m-12,'60 
(B6'221slO)476B 


General  Library 

University  of  California 

Berkeley 


Photomount 

Pamphlet 

Binder 

GayJord  Bros.,  Inc. 

Makers 

Stockton,  Calif. 
PAT.  JAN.  21.  1908 


YB   16861 


U.  C.  BERKELEY  LIBRARIES 


889772 


THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


